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Class: Hash

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ::Enumerable
Inherits: Object
Defined in: hash.c

Overview

A Hash maps each of its unique keys to a specific value.

A Hash has certain similarities to an Array, but:

  • An Array index is always an Integer.

  • A Hash key can be (almost) any object.

Hash Data Syntax

The older syntax for Hash data uses the “hash rocket,” =>:

h = {:foo => 0, :bar => 1, :baz => 2}
h # => {:foo=>0, :bar=>1, :baz=>2}

Alternatively, but only for a Hash key that’s a Symbol, you can use a newer JSON-style syntax, where each bareword becomes a Symbol:

h = {foo: 0, bar: 1, baz: 2}
h # => {:foo=>0, :bar=>1, :baz=>2}

You can also use a String in place of a bareword:

h = {'foo': 0, 'bar': 1, 'baz': 2}
h # => {:foo=>0, :bar=>1, :baz=>2}

And you can mix the styles:

h = {foo: 0, :bar => 1, 'baz': 2}
h # => {:foo=>0, :bar=>1, :baz=>2}

But it’s an error to try the JSON-style syntax for a key that’s not a bareword or a ::String:

# Raises SyntaxError (syntax error, unexpected ':', expecting =>):
h = {0: 'zero'}

Common Uses

You can use a Hash to give names to objects:

person = {name: 'Matz', language: 'Ruby'}
person # => {:name=>"Matz", :language=>"Ruby"}

You can use a Hash to give names to method arguments:

def some_method(hash)
  p hash
end
some_method({foo: 0, bar: 1, baz: 2}) # => {:foo=>0, :bar=>1, :baz=>2}

Note: when the last argument in a method call is a Hash, the curly braces may be omitted:

some_method(foo: 0, bar: 1, baz: 2) # => {:foo=>0, :bar=>1, :baz=>2}

You can use a Hash to initialize an object:

class Dev
  attr_accessor :name, :language
  def initialize(hash)
    self.name = hash[:name]
    self.language = hash[:language]
  end
end
matz = Dev.new(name: 'Matz', language: 'Ruby')
matz # => #<Dev: @name="Matz", @language="Ruby">

Creating a Hash

Here are three ways to create a Hash:

  • Method .new

  • Method Hash[]

  • Literal form: {}.

You can create a Hash by calling method .new.

Create an empty Hash:

h = Hash.new
h # => {}
h.class # => Hash

You can create a Hash by calling method .[].

Create an empty Hash:

h = Hash[]
h # => {}

Create a Hash with initial entries:

h = Hash[foo: 0, bar: 1, baz: 2]
h # => {:foo=>0, :bar=>1, :baz=>2}

You can create a Hash by using its literal form (curly braces).

Create an empty Hash:

h = {}
h # => {}

Create a Hash with initial entries:

h = {foo: 0, bar: 1, baz: 2}
h # => {:foo=>0, :bar=>1, :baz=>2}

Hash Value Basics

The simplest way to retrieve a Hash value (instance method #[]):

h = {foo: 0, bar: 1, baz: 2}
h[:foo] # => 0

The simplest way to create or update a Hash value (instance method #[]=):

h = {foo: 0, bar: 1, baz: 2}
h[:bat] = 3 # => 3
h # => {:foo=>0, :bar=>1, :baz=>2, :bat=>3}
h[:foo] = 4 # => 4
h # => {:foo=>4, :bar=>1, :baz=>2, :bat=>3}

The simplest way to delete a Hash entry (instance method #delete):

h = {foo: 0, bar: 1, baz: 2}
h.delete(:bar) # => 1
h # => {:foo=>0, :baz=>2}

Entry Order

A Hash object presents its entries in the order of their creation. This is seen in:

A new Hash has its initial ordering per the given entries:

h = Hash[foo: 0, bar: 1]
h # => {:foo=>0, :bar=>1}

New entries are added at the end:

h[:baz] = 2
h # => {:foo=>0, :bar=>1, :baz=>2}

Updating a value does not affect the order:

h[:baz] = 3
h # => {:foo=>0, :bar=>1, :baz=>3}

But re-creating a deleted entry can affect the order:

h.delete(:foo)
h[:foo] = 5
h # => {:bar=>1, :baz=>3, :foo=>5}

Hash Keys

Hash Key Equivalence

Two objects are treated as the same hash key when their #hash value is identical and the two objects are #eql? to each other.

Modifying an Active Hash Key

Modifying a Hash key while it is in use damages the hash’s index.

This Hash has keys that are Arrays:

a0 = [ :foo, :bar ]
a1 = [ :baz, :bat ]
h = {a0 => 0, a1 => 1}
h.include?(a0) # => true
h[a0] # => 0
a0.hash # => 110002110

Modifying array element a0[0] changes its hash value:

a0[0] = :bam
a0.hash # => 1069447059

And damages the Hash index:

h.include?(a0) # => false
h[a0] # => nil

You can repair the hash index using method #rehash:

h.rehash # => {[:bam, :bar]=>0, [:baz, :bat]=>1}
h.include?(a0) # => true
h[a0] # => 0

A String key is always safe. That’s because an unfrozen String passed as a key will be replaced by a duplicated and frozen String:

s = 'foo'
s.frozen? # => false
h = {s => 0}
first_key = h.keys.first
first_key.frozen? # => true

User-Defined Hash Keys

To be useable as a Hash key, objects must implement the methods #hash and #eql?. Note: this requirement does not apply if the Hash uses #compare_by_id since comparison will then rely on the keys’ object id instead of #hash and #eql?.

Object defines basic implementation for #hash and eq? that makes each object a distinct key. Typically, user-defined classes will want to override these methods to provide meaningful behavior, or for example inherit Struct that has useful definitions for these.

A typical implementation of #hash is based on the object’s data while #eql? is usually aliased to the overridden #== method:

class Book
  attr_reader :author, :title

  def initialize(author, title)
    @author = author
    @title = title
  end

  def ==(other)
    self.class === other &&
      other.author == @author &&
      other.title == @title
  end

  alias eql? ==

  def hash
    @author.hash ^ @title.hash # XOR
  end
end

book1 = Book.new 'matz', 'Ruby in a Nutshell'
book2 = Book.new 'matz', 'Ruby in a Nutshell'

reviews = {}

reviews[book1] = 'Great reference!'
reviews[book2] = 'Nice and compact!'

reviews.length #=> 1

Default Values

The methods #[], #values_at and #dig need to return the value associated to a certain key. When that key is not found, that value will be determined by its default proc (if any) or else its default (initially nil).

You can retrieve the default value with method #default:

h = Hash.new
h.default # => nil

You can set the default value by passing an argument to method .new or with method #default=

h = Hash.new(-1)
h.default # => -1
h.default = 0
h.default # => 0

This default value is returned for #[], #values_at and #dig when a key is not found:

counts = {foo: 42}
counts.default # => nil (default)
counts[:foo] = 42
counts[:bar] # => nil
counts.default = 0
counts[:bar] # => 0
counts.values_at(:foo, :bar, :baz) # => [42, 0, 0]
counts.dig(:bar) # => 0

Note that the default value is used without being duplicated. It is not advised to set the default value to a mutable object:

synonyms = Hash.new([])
synonyms[:hello] # => []
synonyms[:hello] << :hi # => [:hi], but this mutates the default!
synonyms.default # => [:hi]
synonyms[:world] << :universe
synonyms[:world] # => [:hi, :universe], oops
synonyms.keys # => [], oops

To use a mutable object as default, it is recommended to use a default proc

Default Proc

When the default proc for a Hash is set (i.e., not nil), the default value returned by method #[] is determined by the default proc alone.

You can retrieve the default proc with method #default_proc:

h = Hash.new
h.default_proc # => nil

You can set the default proc by calling .new with a block or calling the method #default_proc=

h = Hash.new { |hash, key| "Default value for #{key}" }
h.default_proc.class # => Proc
h.default_proc = proc { |hash, key| "Default value for #{key.inspect}" }
h.default_proc.class # => Proc

When the default proc is set (i.e., not nil) and method #[] is called with with a non-existent key, #[] calls the default proc with both the Hash object itself and the missing key, then returns the proc’s return value:

h = Hash.new { |hash, key| "Default value for #{key}" }
h[:nosuch] # => "Default value for nosuch"

Note that in the example above no entry for key :nosuch is created:

h.include?(:nosuch) # => false

However, the proc itself can add a new entry:

synonyms = Hash.new { |hash, key| hash[key] = [] }
synonyms.include?(:hello) # => false
synonyms[:hello] << :hi # => [:hi]
synonyms[:world] << :universe # => [:universe]
synonyms.keys # => [:hello, :world]

Note that setting the default proc will clear the default value and vice versa.

Class Method Summary

Instance Attribute Summary

Instance Method Summary

::Enumerable - Included

#all?

Passes each element of the collection to the given block.
#any?

Passes each element of the collection to the given block.
#chain

Returns an enumerator object generated from this enumerator and given enumerables.
#chunk

Enumerates over the items, chunking them together based on the return value of the block.
#chunk_while

Creates an enumerator for each chunked elements.
#collect

Alias for Enumerable#map.
#collect_concat

Alias for Enumerable#flat_map.
#count

Returns the number of items in enum through enumeration.
#cycle

Calls block for each element of enum repeatedly n times or forever if none or nil is given.
#detect

Alias for Enumerable#find.
#drop

Drops first n elements from enum, and returns rest elements in an array.
#drop_while

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.
#each_cons

Iterates the given block for each array of consecutive <n> elements.
#each_entry

Calls block once for each element in self, passing that element as a parameter, converting multiple values from yield to an array.
#each_slice

Iterates the given block for each slice of <n> elements.
#each_with_index

Calls block with two arguments, the item and its index, for each item in enum.
#each_with_object

Iterates the given block for each element with an arbitrary object given, and returns the initially given object.
#entries

Alias for Enumerable#to_a.
#filter

Returns an array containing all elements of enum for which the given block returns a true value.
#filter_map

Returns a new array containing the truthy results (everything except false or nil) of running the block for every element in enum.
#find

Passes each entry in enum to block.
#find_all

Alias for Enumerable#filter.
#find_index

Compares each entry in enum with value or passes to block.
#first

Returns the first element, or the first n elements, of the enumerable.
#flat_map

Returns a new array with the concatenated results of running block once for every element in enum.
#grep

Returns an array of every element in enum for which Pattern === element.
#grep_v

Inverted version of Enumerable#grep.
#group_by

Groups the collection by result of the block.
#include?

Alias for Enumerable#member?.
#inject

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.
#lazy

Returns an ::Enumerator::Lazy, which redefines most ::Enumerable methods to postpone enumeration and enumerate values only on an as-needed basis.
#map

Returns a new array with the results of running block once for every element in enum.
#max

Returns the object in enum with the maximum value.
#max_by

Returns the object in enum that gives the maximum value from the given block.
#member?

Returns true if any member of enum equals obj.
#min

Returns the object in enum with the minimum value.
#min_by

Returns the object in enum that gives the minimum value from the given block.
#minmax

Returns a two element array which contains the minimum and the maximum value in the enumerable.
#minmax_by

Returns a two element array containing the objects in enum that correspond to the minimum and maximum values respectively from the given block.
#none?

Passes each element of the collection to the given block.
#one?

Passes each element of the collection to the given block.
#partition

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.
#reduce

Alias for Enumerable#inject.
#reject

Returns an array for all elements of enum for which the given block returns false.
#reverse_each

Builds a temporary array and traverses that array in reverse order.
#select

Alias for Enumerable#filter.
#slice_after

Creates an enumerator for each chunked elements.
#slice_before

Creates an enumerator for each chunked elements.
#slice_when

Creates an enumerator for each chunked elements.
#sort

Returns an array containing the items in enum sorted.
#sort_by

Sorts enum using a set of keys generated by mapping the values in enum through the given block.
#sum

Returns the sum of elements in an ::Enumerable.
#take

Returns first n elements from enum.
#take_while

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.
#tally

Tallies the collection, i.e., counts the occurrences of each element.
#to_a

Returns an array containing the items in enum.
#to_h

Returns the result of interpreting enum as a list of [key, value] pairs.
#uniq

Returns a new array by removing duplicate values in self.
#zip

Takes one element from enum and merges corresponding elements from each args.

Constructor Details

.new(default_value = nil) ⇒ Hash .new {|hash, key| ... } ⇒ Hash

Returns a new empty Hash object.

The initial default value and initial default proc for the new hash depend on which form above was used. See Default Values.

If neither an argument nor a block given, initializes both the default value and the default proc to nil:

h = Hash.new
h.default # => nil
h.default_proc # => nil

If argument default_value given but no block given, initializes the default value to the given default_value and the default proc to nil:

h = Hash.new(false)
h.default # => false
h.default_proc # => nil

If a block given but no argument, stores the block as the default proc and sets the default value to nil:

h = Hash.new {|hash, key| "Default value for #{key}" }
h.default # => nil
h.default_proc.class # => Proc
h[:nosuch] # => "Default value for nosuch"
[ GitHub ] 

  


# File 'hash.c', line 1771



static VALUE
rb_hash_initialize(int argc, VALUE *argv, VALUE hash)
{
    VALUE ifnone;

    rb_hash_modify(hash);
    if (rb_block_given_p()) {
	rb_check_arity(argc, 0, 0);
	ifnone = rb_block_proc();
	SET_PROC_DEFAULT(hash, ifnone);
    }
    else {
	rb_check_arity(argc, 0, 1);
	ifnone = argc == 0 ? Qnil : argv[0];
	RHASH_SET_IFNONE(hash, ifnone);
    }

    return hash;
}


  







Class Method Details



  

    

      .[]  ⇒ Hash 
      .[](hash)  ⇒ Hash 
      .[]([*2_element_arrays] )  ⇒ Hash 
      .[](*objects)  ⇒ Hash 
    

  



  

    

Returns a new Hash object populated with the given objects, if any. See .new.



With no argument, returns a new empty Hash.



When the single given argument is a Hash, returns a new Hash populated with the entries from the given Hash.



h = {foo: 0, bar: 1, baz: 2}
Hash[h] # => {:foo=>0, :bar=>1, :baz=>2}



When the single given argument is an Array of 2-element Arrays, returns a new Hash object wherein each 2-element array forms a key-value entry:



Hash[ [ [:foo, 0], [:bar, 1] ] ] # => {:foo=>0, :bar=>1}



When the argument count is an even number; returns a new Hash object wherein each successive pair of arguments has become a key-value entry:



Hash[:foo, 0, :bar, 1] # => {:foo=>0, :bar=>1}



Raises an exception if the argument list does not conform to any of the above.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 1820



static VALUE
rb_hash_s_create(int argc, VALUE *argv, VALUE klass)
{
    VALUE hash, tmp;

    if (argc == 1) {
        tmp = rb_hash_s_try_convert(Qnil, argv[0]);
	if (!NIL_P(tmp)) {
	    hash = hash_alloc(klass);
            hash_copy(hash, tmp);
	    return hash;
	}

	tmp = rb_check_array_type(argv[0]);
	if (!NIL_P(tmp)) {
	    long i;

	    hash = hash_alloc(klass);
	    for (i = 0; i < RARRAY_LEN(tmp); ++i) {
		VALUE e = RARRAY_AREF(tmp, i);
		VALUE v = rb_check_array_type(e);
		VALUE key, val = Qnil;

		if (NIL_P(v)) {
		    rb_raise(rb_eArgError, "wrong element type %s at %ld (expected array)",
			     rb_builtin_class_name(e), i);
		}
		switch (RARRAY_LEN(v)) {
		  default:
		    rb_raise(rb_eArgError, "invalid number of elements (%ld for 1..2)",
			     RARRAY_LEN(v));
		  case 2:
		    val = RARRAY_AREF(v, 1);
		  case 1:
		    key = RARRAY_AREF(v, 0);
		    rb_hash_aset(hash, key, val);
		}
	    }
	    return hash;
	}
    }
    if (argc % 2 != 0) {
	rb_raise(rb_eArgError, "odd number of arguments for Hash");
    }

    hash = hash_alloc(klass);
    rb_hash_bulk_insert(argc, argv, hash);
    hash_verify(hash);
    return hash;
}


  








  

    .ruby2_keywords_hash(hash)  ⇒ Hash   



  

    

Duplicates a given hash and adds a ruby2_keywords flag. This method is not for casual use; debugging, researching, and some truly necessary cases like deserialization of arguments.



h = {k: 1}
h = Hash.ruby2_keywords_hash(h)
def foo(k: 42)
  k
end
foo(*[h]) #=> 1 with neither a warning or an error


  



  [ GitHub ]


  

  


# File 'hash.c', line 1940



static VALUE
rb_hash_s_ruby2_keywords_hash(VALUE dummy, VALUE hash)
{
    Check_Type(hash, T_HASH);
    hash = rb_hash_dup(hash);
    RHASH(hash)->basic.flags |= RHASH_PASS_AS_KEYWORDS;
    return hash;
}


  








  

    .ruby2_keywords_hash?(hash)  ⇒ Boolean   



  

    

Checks if a given hash is flagged by Module#ruby2_keywords (or Proc#ruby2_keywords). This method is not for casual use; debugging, researching, and some truly necessary cases like serialization of arguments.



ruby2_keywords def foo(*args)
  Hash.ruby2_keywords_hash?(args.last)
end
foo(k: 1)   #=> true
foo({k: 1}) #=> false


  



  [ GitHub ]


  

  


# File 'hash.c', line 1918



static VALUE
rb_hash_s_ruby2_keywords_hash_p(VALUE dummy, VALUE hash)
{
    Check_Type(hash, T_HASH);
    return (RHASH(hash)->basic.flags & RHASH_PASS_AS_KEYWORDS) ? Qtrue : Qfalse;
}


  








  

    .try_convert(obj)  ⇒ Object, ...   



  

    

If obj is a Hash object, returns obj.



Otherwise if obj responds to :to_hash, calls obj.to_hash and returns the result.



Returns nil if obj does not respond to :to_hash



Raises an exception unless obj.to_hash returns a Hash object.


  



  [ GitHub ]


  

  


# File 'hash.c', line 1897



static VALUE
rb_hash_s_try_convert(VALUE dummy, VALUE hash)
{
    return rb_check_hash_type(hash);
}


  







Instance Attribute Details



  

    #compare_by_identity  ⇒ self  (readonly)  



  

    

Sets self to consider only identity in comparing keys; two keys are considered the same only if they are the same object; returns self.



By default, these two object are considered to be the same key, so s1 will overwrite s0:



s0 = 'x'
s1 = 'x'
h = {}
h.compare_by_identity? # => false
h[s0] = 0
h[s1] = 1
h # => {"x"=>1}



After calling #compare_by_identity, the keys are considered to be different, and therefore do not overwrite each other:



h = {}
h.compare_by_identity # => {}
h.compare_by_identity? # => true
h[s0] = 0
h[s1] = 1
h # => {"x"=>0, "x"=>1}


  



  [ GitHub ]


  

  


# File 'hash.c', line 4419



static VALUE
rb_hash_compare_by_id(VALUE hash)
{
    VALUE tmp;
    st_table *identtable;

    if (rb_hash_compare_by_id_p(hash)) return hash;

    rb_hash_modify_check(hash);
    ar_force_convert_table(hash, __FILE__, __LINE__);
    HASH_ASSERT(RHASH_ST_TABLE_P(hash));

    tmp = hash_alloc(0);
    identtable = rb_init_identtable_with_size(RHASH_SIZE(hash));
    RHASH_ST_TABLE_SET(tmp, identtable);
    rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
    st_free_table(RHASH_ST_TABLE(hash));
    RHASH_ST_TABLE_SET(hash, identtable);
    RHASH_ST_CLEAR(tmp);
    rb_gc_force_recycle(tmp);

    return hash;
}


  








  

    #compare_by_identity?  ⇒ Boolean  (readonly)  



  

    

Returns true if #compare_by_identity has been called, false otherwise.


  



  [ GitHub ]


  

  


# File 'hash.c', line 4450



MJIT_FUNC_EXPORTED VALUE
rb_hash_compare_by_id_p(VALUE hash)
{
    if (RHASH_ST_TABLE_P(hash) && RHASH_ST_TABLE(hash)->type == &identhash) {
	return Qtrue;
    }
    else {
        return Qfalse;
    }
}


  








  

    #default_proc  ⇒ Proc?  (rw)  



  

    

Returns the default proc for self (see Default Values):



h = {}
h.default_proc # => nil
h.default_proc = proc {|hash, key| "Default value for #{key}" }
h.default_proc.class # => Proc


  



  [ GitHub ]


  

  


# File 'hash.c', line 2229



static VALUE
rb_hash_default_proc(VALUE hash)
{
    if (FL_TEST(hash, RHASH_PROC_DEFAULT)) {
	return RHASH_IFNONE(hash);
    }
    return Qnil;
}


  








  

    #default_proc=(proc)  ⇒ Proc  (rw)  



  

    

Sets the default proc for self to proc: (see Default Values):



h = {}
h.default_proc # => nil
h.default_proc = proc { |hash, key| "Default value for #{key}" }
h.default_proc.class # => Proc
h.default_proc = nil
h.default_proc # => nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 2252



VALUE
rb_hash_set_default_proc(VALUE hash, VALUE proc)
{
    VALUE b;

    rb_hash_modify_check(hash);
    if (NIL_P(proc)) {
	SET_DEFAULT(hash, proc);
	return proc;
    }
    b = rb_check_convert_type_with_id(proc, T_DATA, "Proc", idTo_proc);
    if (NIL_P(b) || !rb_obj_is_proc(b)) {
	rb_raise(rb_eTypeError,
		 "wrong default_proc type %s (expected Proc)",
		 rb_obj_classname(proc));
    }
    proc = b;
    SET_PROC_DEFAULT(hash, proc);
    return proc;
}


  








  

    #empty?  ⇒ Boolean  (readonly)  



  

    

Returns true if there are no hash entries, false otherwise:



{}.empty? # => true
{foo: 0, bar: 1, baz: 2}.empty? # => false


  



  [ GitHub ]


  

  


# File 'hash.c', line 3020



static VALUE
rb_hash_empty_p(VALUE hash)
{
    return RHASH_EMPTY_P(hash) ? Qtrue : Qfalse;
}


  







Instance Method Details



  

    #<(other_hash)  ⇒ Boolean   



  

    

Returns true if #hash is a proper subset of other_hash, false otherwise:



h1 = {foo: 0, bar: 1}
h2 = {foo: 0, bar: 1, baz: 2}
h1 < h2 # => true
h2 < h1 # => false
h1 < h1 # => false


  



  [ GitHub ]


  

  


# File 'hash.c', line 4661



static VALUE
rb_hash_lt(VALUE hash, VALUE other)
{
    other = to_hash(other);
    if (RHASH_SIZE(hash) >= RHASH_SIZE(other)) return Qfalse;
    return hash_le(hash, other);
}


  








  

    #<=(other_hash)  ⇒ Boolean   



  

    

Returns true if #hash is a subset of other_hash, false otherwise:



h1 = {foo: 0, bar: 1}
h2 = {foo: 0, bar: 1, baz: 2}
h1 <= h2 # => true
h2 <= h1 # => false
h1 <= h1 # => true


  



  [ GitHub ]


  

  


# File 'hash.c', line 4642



static VALUE
rb_hash_le(VALUE hash, VALUE other)
{
    other = to_hash(other);
    if (RHASH_SIZE(hash) > RHASH_SIZE(other)) return Qfalse;
    return hash_le(hash, other);
}


  








  

    #==(object)  ⇒ Boolean   



  

    

Returns true if all of the following are true:


  • 

    object is a Hash object.
    

  • 

    #hash and object have the same keys (regardless of order).
    

  • 

    For each key #key, hash[key] == object[key].
    




Otherwise, returns false.



Equal:



h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1, baz: 2}
h1 == h2 # => true
h3 = {baz: 2, bar: 1, foo: 0}
h1 == h3 # => true


  



  [ GitHub ]


  

  


# File 'hash.c', line 3797



static VALUE
rb_hash_equal(VALUE hash1, VALUE hash2)
{
    return hash_equal(hash1, hash2, FALSE);
}


  








  

    #>(other_hash)  ⇒ Boolean   



  

    

Returns true if #hash is a proper superset of other_hash, false otherwise:



h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1}
h1 > h2 # => true
h2 > h1 # => false
h1 > h1 # => false


  



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# File 'hash.c', line 4699



static VALUE
rb_hash_gt(VALUE hash, VALUE other)
{
    other = to_hash(other);
    if (RHASH_SIZE(hash) <= RHASH_SIZE(other)) return Qfalse;
    return hash_le(other, hash);
}


  








  

    #>=(other_hash)  ⇒ Boolean   



  

    

Returns true if #hash is a superset of other_hash, false otherwise:



h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1}
h1 >= h2 # => true
h2 >= h1 # => false
h1 >= h1 # => true


  



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# File 'hash.c', line 4680



static VALUE
rb_hash_ge(VALUE hash, VALUE other)
{
    other = to_hash(other);
    if (RHASH_SIZE(hash) < RHASH_SIZE(other)) return Qfalse;
    return hash_le(other, hash);
}


  








  

    #[](key)  ⇒ value   



  

    

Returns the value associated with the given #key, if found:



h = {foo: 0, bar: 1, baz: 2}
h[:foo] # => 0



If #key is not found, returns a default value (see Default Values):



h = {foo: 0, bar: 1, baz: 2}
h[:nosuch] # => nil


  



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# File 'hash.c', line 2064



VALUE
rb_hash_aref(VALUE hash, VALUE key)
{
    st_data_t val;

    if (hash_stlike_lookup(hash, key, &val)) {
        return (VALUE)val;
    }
    else {
        return rb_hash_default_value(hash, key);
    }
}


  








  

    

      #[]=(key, value)  ⇒ value 
      #store(key, value)  
    

    Also known as: #store
  



  

    

#store is an alias for []=.



Associates the given value with the given #key; returns value.



If the given #key exists, replaces its value with the given value; the ordering is not affected (see Entry Order):



h = {foo: 0, bar: 1}
h[:foo] = 2 # => 2
h.store(:bar, 3) # => 3
h # => {:foo=>2, :bar=>3}



If #key does not exist, adds the #key and value; the new entry is last in the order (see Entry Order):



h = {foo: 0, bar: 1}
h[:baz] = 2 # => 2
h.store(:bat, 3) # => 3
h # => {:foo=>0, :bar=>1, :baz=>2, :bat=>3}


  





  


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# File 'hash.c', line 2919



VALUE
rb_hash_aset(VALUE hash, VALUE key, VALUE val)
{
    int iter_lev = RHASH_ITER_LEV(hash);

    rb_hash_modify(hash);

    if (RHASH_TABLE_NULL_P(hash)) {
	if (iter_lev > 0) no_new_key();
        ar_alloc_table(hash);
    }

    if (RHASH_TYPE(hash) == &identhash || rb_obj_class(key) != rb_cString) {
	RHASH_UPDATE_ITER(hash, iter_lev, key, hash_aset, val);
    }
    else {
	RHASH_UPDATE_ITER(hash, iter_lev, key, hash_aset_str, val);
    }
    return val;
}


  








  

    

      #any?  ⇒ Boolean 
      #any?(object)  ⇒ Boolean 
      #any? {|key, value| ... } ⇒ Boolean 
    

  



  

    

Returns true if any element satisfies a given criterion; false otherwise.



With no argument and no block, returns true if self is non-empty; false if empty.



With argument object and no block, returns true if for any key #key h.assoc(key) == object:



h = {foo: 0, bar: 1, baz: 2}
h.any?([:bar, 1]) # => true
h.any?([:bar, 0]) # => false
h.any?([:baz, 1]) # => false



With no argument and a block, calls the block with each key-value pair; returns true if the block returns any truthy value, false otherwise:



h = {foo: 0, bar: 1, baz: 2}
h.any? {|key, value| value < 3 } # => true
h.any? {|key, value| value > 3 } # => false


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 4543



static VALUE
rb_hash_any_p(int argc, VALUE *argv, VALUE hash)
{
    VALUE args[2];
    args[0] = Qfalse;

    rb_check_arity(argc, 0, 1);
    if (RHASH_EMPTY_P(hash)) return Qfalse;
    if (argc) {
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
	args[1] = argv[0];

	rb_hash_foreach(hash, any_p_i_pattern, (VALUE)args);
    }
    else {
	if (!rb_block_given_p()) {
	    /* yields pairs, never false */
	    return Qtrue;
	}
        if (rb_block_pair_yield_optimizable())
	    rb_hash_foreach(hash, any_p_i_fast, (VALUE)args);
	else
	    rb_hash_foreach(hash, any_p_i, (VALUE)args);
    }
    return args[0];
}


  








  

    #assoc(key)  ⇒ Array?   



  

    

If the given #key is found, returns a 2-element Array containing that key and its value:



h = {foo: 0, bar: 1, baz: 2}
h.assoc(:bar) # => [:bar, 1]



Returns nil if key #key is not found.


  



  [ GitHub ]


  

  


# File 'hash.c', line 4178



VALUE
rb_hash_assoc(VALUE hash, VALUE key)
{
    st_table *table;
    const struct st_hash_type *orighash;
    VALUE args[2];

    if (RHASH_EMPTY_P(hash)) return Qnil;

    ar_force_convert_table(hash, __FILE__, __LINE__);
    HASH_ASSERT(RHASH_ST_TABLE_P(hash));
    table = RHASH_ST_TABLE(hash);
    orighash = table->type;

    if (orighash != &identhash) {
	VALUE value;
	struct reset_hash_type_arg ensure_arg;
	struct st_hash_type assochash;

	assochash.compare = assoc_cmp;
	assochash.hash = orighash->hash;
        table->type = &assochash;
	args[0] = hash;
	args[1] = key;
	ensure_arg.hash = hash;
	ensure_arg.orighash = orighash;
	value = rb_ensure(lookup2_call, (VALUE)&args, reset_hash_type, (VALUE)&ensure_arg);
	if (value != Qundef) return rb_assoc_new(key, value);
    }

    args[0] = key;
    args[1] = Qnil;
    rb_hash_foreach(hash, assoc_i, (VALUE)args);
    return args[1];
}


  








  

    #clear  ⇒ self   



  

    

Removes all hash entries; returns self.


  



  [ GitHub ]


  

  


# File 'hash.c', line 2837



VALUE
rb_hash_clear(VALUE hash)
{
    rb_hash_modify_check(hash);

    if (RHASH_ITER_LEV(hash) > 0) {
        rb_hash_foreach(hash, clear_i, 0);
    }
    else if (RHASH_AR_TABLE_P(hash)) {
        ar_clear(hash);
    }
    else {
        st_clear(RHASH_ST_TABLE(hash));
    }

    return hash;
}


  








  

    #compact  ⇒ Hash   



  

    

Returns a copy of self with all nil-valued entries removed:



h = {foo: 0, bar: nil, baz: 2, bat: nil}
h1 = h.compact
h1 # => {:foo=>0, :baz=>2}


  



  [ GitHub ]


  

  


# File 'hash.c', line 4354



static VALUE
rb_hash_compact(VALUE hash)
{
    VALUE result = rb_hash_new();
    if (!RHASH_EMPTY_P(hash)) {
	rb_hash_foreach(hash, set_if_not_nil, result);
    }
    return result;
}


  








  

    #compact!  ⇒ self?   



  

    

Returns self with all its nil-valued entries removed (in place):



h = {foo: 0, bar: nil, baz: 2, bat: nil}
h.compact! # => {:foo=>0, :baz=>2}



Returns nil if no entries were removed.


  



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# File 'hash.c', line 4375



static VALUE
rb_hash_compact_bang(VALUE hash)
{
    st_index_t n;
    rb_hash_modify_check(hash);
    n = RHASH_SIZE(hash);
    if (n) {
	rb_hash_foreach(hash, delete_if_nil, hash);
        if (n != RHASH_SIZE(hash))
	    return hash;
    }
    return Qnil;
}


  








  

    #deconstruct_keys(keys)  
  

  [ GitHub ]


  

  


# File 'hash.c', line 4732



static VALUE
rb_hash_deconstruct_keys(VALUE hash, VALUE keys)
{
    return hash;
}


  








  

    

      #default  ⇒ Object 
      #default(key)  ⇒ Object 
    

  



  

    

Returns the default value for the given #key. The returned value will be determined either by the default proc or by the default value. See Default Values.



With no argument, returns the current default value:



h = {}
h.default # => nil



If #key is given, returns the default value for #key, regardless of whether that key exists:



h = Hash.new { |hash, key| hash[key] = "No key #{key}"}
h[:foo] = "Hello"
h.default(:foo) # => "No key foo"


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2182



static VALUE
rb_hash_default(int argc, VALUE *argv, VALUE hash)
{
    VALUE ifnone;

    rb_check_arity(argc, 0, 1);
    ifnone = RHASH_IFNONE(hash);
    if (FL_TEST(hash, RHASH_PROC_DEFAULT)) {
	if (argc == 0) return Qnil;
	return call_default_proc(ifnone, hash, argv[0]);
    }
    return ifnone;
}


  








  

    #default=(value)  ⇒ Object   



  

    

Sets the default value to value; returns value:



h = {}
h.default # => nil
h.default = false # => false
h.default # => false



See Default Values.


  



  [ GitHub ]


  

  


# File 'hash.c', line 2209



static VALUE
rb_hash_set_default(VALUE hash, VALUE ifnone)
{
    rb_hash_modify_check(hash);
    SET_DEFAULT(hash, ifnone);
    return ifnone;
}


  








  

    

      #delete(key)  ⇒ value? 
      #delete(key) {|key| ... } ⇒ Object 
    

  



  

    

Deletes the entry for the given #key and returns its associated value.



If no block is given and #key is found, deletes the entry and returns the associated value:



h = {foo: 0, bar: 1, baz: 2}
h.delete(:bar) # => 1
h # => {:foo=>0, :baz=>2}



If no block given and #key is not found, returns nil.



If a block is given and #key is found, ignores the block, deletes the entry, and returns the associated value:



h = {foo: 0, bar: 1, baz: 2}
h.delete(:baz) { |key| raise 'Will never happen'} # => 2
h # => {:foo=>0, :bar=>1}



If a block is given and #key is not found, calls the block and returns the block’s return value:



h = {foo: 0, bar: 1, baz: 2}
h.delete(:nosuch) { |key| "Key #{key} not found" } # => "Key nosuch not found"
h # => {:foo=>0, :bar=>1, :baz=>2}


  





  


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# File 'hash.c', line 2385



static VALUE
rb_hash_delete_m(VALUE hash, VALUE key)
{
    VALUE val;

    rb_hash_modify_check(hash);
    val = rb_hash_delete_entry(hash, key);

    if (val != Qundef) {
	return val;
    }
    else {
	if (rb_block_given_p()) {
	    return rb_yield(key);
	}
	else {
	    return Qnil;
	}
    }
}


  








  

    

      #delete_if {|key, value| ... } ⇒ self 
      #delete_if  ⇒ Enumerator 
    

  



  

    

If a block given, calls the block with each key-value pair; deletes each entry for which the block returns a truthy value; returns self:



h = {foo: 0, bar: 1, baz: 2}
h.delete_if {|key, value| value > 0 } # => {:foo=>0}



If no block given, returns a new Enumerator:



h = {foo: 0, bar: 1, baz: 2}
e = h.delete_if # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:delete_if>
e.each { |key, value| value > 0 } # => {:foo=>0}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2508



VALUE
rb_hash_delete_if(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    if (!RHASH_TABLE_EMPTY_P(hash)) {
        rb_hash_foreach(hash, delete_if_i, hash);
    }
    return hash;
}


  








  

    #dig(key, *identifiers)  ⇒ Object   



  

    

Finds and returns the object in nested objects that is specified by #key and identifiers. The nested objects may be instances of various classes. See Dig Methods.



Nested Hashes:



h = {foo: {bar: {baz: 2}}}
h.dig(:foo) # => {:bar=>{:baz=>2}}
h.dig(:foo, :bar) # => {:bar=>{:baz=>2}}
h.dig(:foo, :bar, :baz) # => 2
h.dig(:foo, :bar, :BAZ) # => nil



Nested Hashes and Arrays:



h = {foo: {bar: [:a, :b, :c]}}
h.dig(:foo, :bar, 2) # => :c



This method will use the default values for keys that are not present:



h = {foo: {bar: [:a, :b, :c]}}
h.dig(:hello) # => nil
h.default_proc = -> (hash, _key) { hash }
h.dig(:hello, :world) # => h
h.dig(:hello, :world, :foo, :bar, 2) # => :c


  



  [ GitHub ]


  

  


# File 'hash.c', line 4601



static VALUE
rb_hash_dig(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    self = rb_hash_aref(self, *argv);
    if (!--argc) return self;
    ++argv;
    return rb_obj_dig(argc, argv, self, Qnil);
}


  








  

    

      #each {|key, value| ... } ⇒ self 
      #each_pair {|key, value| ... } ⇒ self 
      #each  ⇒ Enumerator 
      #each_pair  ⇒ Enumerator 
    

    Also known as: #each_pair
  



  

    

each is an alias for #each_pair.



Calls the given block with each key-value pair; returns self:



h = {foo: 0, bar: 1, baz: 2}
h.each_pair {|key, value| puts "#{key}: #{value}"} # => {:foo=>0, :bar=>1, :baz=>2}



Output:



foo: 0
bar: 1
baz: 2



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.each_pair # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_pair>
h1 = e.each {|key, value| puts "#{key}: #{value}"}
h1 # => {:foo=>0, :bar=>1, :baz=>2}



Output:



foo: 0
bar: 1
baz: 2


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3148



static VALUE
rb_hash_each_pair(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    if (rb_block_pair_yield_optimizable())
	rb_hash_foreach(hash, each_pair_i_fast, 0);
    else
	rb_hash_foreach(hash, each_pair_i, 0);
    return hash;
}


  








  

    

      #each_key {|key| ... } ⇒ self 
      #each_key  ⇒ Enumerator 
    

  



  

    

Calls the given block with each key; returns self:



h = {foo: 0, bar: 1, baz: 2}
h.each_key {|key| puts key }  # => {:foo=>0, :bar=>1, :baz=>2}



Output:



foo
bar
baz



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.each_key # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_key>
h1 = e.each {|key| puts key }
h1 # => {:foo=>0, :bar=>1, :baz=>2}



Output:



foo
bar
baz


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3095



static VALUE
rb_hash_each_key(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_foreach(hash, each_key_i, 0);
    return hash;
}


  








  

    

      #each {|key, value| ... } ⇒ self 
      #each_pair {|key, value| ... } ⇒ self 
      #each  ⇒ Enumerator 
      #each_pair  ⇒ Enumerator 
    

  



  

    

Alias for #each.


  





  








  

    

      #each_value {|value| ... } ⇒ self 
      #each_value  ⇒ Enumerator 
    

  



  

    

Calls the given block with each value; returns self:



h = {foo: 0, bar: 1, baz: 2}
h.each_value {|value| puts value } # => {:foo=>0, :bar=>1, :baz=>2}



Output:



0
1
2



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.each_value # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_value>
h1 = e.each {|value| puts value }
h1 # => {:foo=>0, :bar=>1, :baz=>2}



Output:



0
1
2


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3057



static VALUE
rb_hash_each_value(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_foreach(hash, each_value_i, 0);
    return hash;
}


  








  

    #eql?(object)  ⇒ Boolean   



  

    

Returns true if all of the following are true:


  • 

    object is a Hash object.
    

  • 

    #hash and object have the same keys (regardless of order).
    

  • 

    For each key #key, h[key] eql? object[key].
    




Otherwise, returns false.



Equal:



h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1, baz: 2}
h1.eql? h2 # => true
h3 = {baz: 2, bar: 1, foo: 0}
h1.eql? h3 # => true


  



  [ GitHub ]


  

  


# File 'hash.c', line 3822



static VALUE
rb_hash_eql(VALUE hash1, VALUE hash2)
{
    return hash_equal(hash1, hash2, TRUE);
}


  








  

    #except(*keys)  ⇒ Hash   



  

    

Returns a new Hash excluding entries for the given #keys:



h = { a: 100, b: 200, c: 300 }
h.except(:a)          #=> {:b=>200, :c=>300}



Any given #keys that are not found are ignored.


  



  [ GitHub ]


  

  


# File 'hash.c', line 2640



static VALUE
rb_hash_except(int argc, VALUE *argv, VALUE hash)
{
    int i;
    VALUE key, result;

    result = hash_alloc(rb_cHash);
    hash_copy(result, hash);

    for (i = 0; i < argc; i++) {
        key = argv[i];
        rb_hash_delete(result, key);
    }

    return result;
}


  








  

    

      #fetch(key)  ⇒ Object 
      #fetch(key, default_value)  ⇒ Object 
      #fetch(key) {|key| ... } ⇒ Object 
    

  



  

    

Returns the value for the given #key, if found.



h = {foo: 0, bar: 1, baz: 2}
h.fetch(:bar) # => 1



If #key is not found and no block was given, returns default_value:



{}.fetch(:nosuch, :default) # => :default
{}.fetch(:nosuch) # => nil



If #key is not found and a block was given, yields #key to the block and returns the block’s return value:



{}.fetch(:nosuch) {|key| "No key #{key}"} # => "No key nosuch"



Raises KeyError if neither default_value nor a block was given.



Note that this method does not use the values of either #default or #default_proc.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2120



static VALUE
rb_hash_fetch_m(int argc, VALUE *argv, VALUE hash)
{
    VALUE key;
    st_data_t val;
    long block_given;

    rb_check_arity(argc, 1, 2);
    key = argv[0];

    block_given = rb_block_given_p();
    if (block_given && argc == 2) {
	rb_warn("block supersedes default value argument");
    }

    if (hash_stlike_lookup(hash, key, &val)) {
        return (VALUE)val;
    }
    else {
        if (block_given) {
            return rb_yield(key);
        }
        else if (argc == 1) {
            VALUE desc = rb_protect(rb_inspect, key, 0);
            if (NIL_P(desc)) {
                desc = rb_any_to_s(key);
            }
            desc = rb_str_ellipsize(desc, 65);
            rb_key_err_raise(rb_sprintf("key not found: %"PRIsVALUE, desc), hash, key);
        }
        else {
            return argv[1];
        }
    }
}


  








  

    

      #fetch_values(*keys)  ⇒ Array 
      #fetch_values(*keys) {|key| ... } ⇒ Array 
    

  



  

    

Returns a new Array containing the values associated with the given keys *keys:



h = {foo: 0, bar: 1, baz: 2}
h.fetch_values(:baz, :foo) # => [2, 0]



Returns a new empty Array if no arguments given.



When a block is given, calls the block with each missing key, treating the block’s return value as the value for that key:



h = {foo: 0, bar: 1, baz: 2}
values = h.fetch_values(:bar, :foo, :bad, :bam) {|key| key.to_s}
values # => [1, 0, "bad", "bam"]



When no block is given, raises an exception if any given key is not found.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2702



static VALUE
rb_hash_fetch_values(int argc, VALUE *argv, VALUE hash)
{
    VALUE result = rb_ary_new2(argc);
    long i;

    for (i=0; i<argc; i++) {
	rb_ary_push(result, rb_hash_fetch(hash, argv[i]));
    }
    return result;
}


  








  

    

      #select {|key, value| ... } ⇒ Hash 
      #select  ⇒ Enumerator 
    

    Also known as: #select
  



  

    

filter is an alias for #select.



Returns a new Hash object whose entries are those for which the block returns a truthy value:



h = {foo: 0, bar: 1, baz: 2}
h.select {|key, value| value < 2 } # => {:foo=>0, :bar=>1}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.select # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select>
e.each {|key, value| value < 2 } # => {:foo=>0, :bar=>1}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2740



static VALUE
rb_hash_select(VALUE hash)
{
    VALUE result;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    result = rb_hash_new();
    if (!RHASH_EMPTY_P(hash)) {
	rb_hash_foreach(hash, select_i, result);
    }
    return result;
}


  








  

    

      #select! {|key, value| ... } ⇒ self? 
      #select!  ⇒ Enumerator 
    

    Also known as: #select!
  



  

    

filter! is an alias for #select!.



Returns self, whose entries are those for which the block returns a truthy value:



h = {foo: 0, bar: 1, baz: 2}
h.select! {|key, value| value < 2 }  => {:foo=>0, :bar=>1}



Returns nil if no entries were removed.



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.select!  # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select!>
e.each { |key, value| value < 2 } # => {:foo=>0, :bar=>1}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2782



static VALUE
rb_hash_select_bang(VALUE hash)
{
    st_index_t n;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    n = RHASH_SIZE(hash);
    if (!n) return Qnil;
    rb_hash_foreach(hash, keep_if_i, hash);
    if (n == RHASH_SIZE(hash)) return Qnil;
    return hash;
}


  








  

    

      #flatten  ⇒ Array 
      #flatten(level)  ⇒ Array 
    

  



  

    

Returns a new Array object that is a 1-dimensional flattening of self.





By default, nested Arrays are not flattened:



h = {foo: 0, bar: [:bat, 3], baz: 2}
h.flatten # => [:foo, 0, :bar, [:bat, 3], :baz, 2]



Takes the depth of recursive flattening from Integer argument level:



h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]}
h.flatten(1) # => [:foo, 0, :bar, [:bat, [:baz, [:bat]]]]
h.flatten(2) # => [:foo, 0, :bar, :bat, [:baz, [:bat]]]
h.flatten(3) # => [:foo, 0, :bar, :bat, :baz, [:bat]]
h.flatten(4) # => [:foo, 0, :bar, :bat, :baz, :bat]



When level is negative, flattens all nested Arrays:



h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]}
h.flatten(-1) # => [:foo, 0, :bar, :bat, :baz, :bat]
h.flatten(-2) # => [:foo, 0, :bar, :bat, :baz, :bat]



When level is zero, returns the equivalent of #to_a :



h = {foo: 0, bar: [:bat, 3], baz: 2}
h.flatten(0) # => [[:foo, 0], [:bar, [:bat, 3]], [:baz, 2]]
h.flatten(0) == h.to_a # => true


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 4293



static VALUE
rb_hash_flatten(int argc, VALUE *argv, VALUE hash)
{
    VALUE ary;

    rb_check_arity(argc, 0, 1);

    if (argc) {
	int level = NUM2INT(argv[0]);

	if (level == 0) return rb_hash_to_a(hash);

	ary = rb_ary_new_capa(RHASH_SIZE(hash) * 2);
	rb_hash_foreach(hash, flatten_i, ary);
	level--;

	if (level > 0) {
	    VALUE ary_flatten_level = INT2FIX(level);
	    rb_funcallv(ary, id_flatten_bang, 1, &ary_flatten_level);
	}
	else if (level < 0) {
	    /* flatten recursively */
	    rb_funcallv(ary, id_flatten_bang, 0, 0);
	}
    }
    else {
	ary = rb_ary_new_capa(RHASH_SIZE(hash) * 2);
	rb_hash_foreach(hash, flatten_i, ary);
    }

    return ary;
}


  








  

    

      #include?(key)  ⇒ Boolean 
      #has_key?(key)  ⇒ Boolean 
      #key?(key)  ⇒ Boolean 
      #member?(key)  ⇒ Boolean 
    

  



  

    

Alias for #key?.


  





  








  

    

      #value?(value)  ⇒ Boolean 
      #has_value?(value)  ⇒ Boolean 
    

  



  

    

Alias for #value?.


  





  








  

    #hash  ⇒ Integer   



  

    

Returns the Integer hash-code for the hash.



Two Hash objects have the same hash-code if their content is the same (regardless or order):



h1 = {foo: 0, bar: 1, baz: 2}
h2 = {baz: 2, bar: 1, foo: 0}
h2.hash == h1.hash # => true
h2.eql? h1 # => true


  



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# File 'hash.c', line 3854



static VALUE
rb_hash_hash(VALUE hash)
{
    st_index_t size = RHASH_SIZE(hash);
    st_index_t hval = rb_hash_start(size);
    hval = rb_hash_uint(hval, (st_index_t)rb_hash_hash);
    if (size) {
	rb_hash_foreach(hash, hash_i, (VALUE)&hval);
    }
    hval = rb_hash_end(hval);
    return ST2FIX(hval);
}


  








  

    

      #include?(key)  ⇒ Boolean 
      #has_key?(key)  ⇒ Boolean 
      #key?(key)  ⇒ Boolean 
      #member?(key)  ⇒ Boolean 
    

  



  

    

Alias for #key?.


  





  








  

    

      #replace(other_hash)  ⇒ self 
      #initialize_copy(other_hash)  ⇒ self 
    

  



  

    

Alias for #replace.


  





  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

  



  

    

Alias for #to_s.


  





  








  

    #invert  ⇒ Hash   



  

    

Returns a new Hash object with the each key-value pair inverted:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.invert
h1 # => {0=>:foo, 1=>:bar, 2=>:baz}



Overwrites any repeated new keys: (see Entry Order):



h = {foo: 0, bar: 0, baz: 0}
h.invert # => {0=>:baz}


  



  [ GitHub ]


  

  


# File 'hash.c', line 3889



static VALUE
rb_hash_invert(VALUE hash)
{
    VALUE h = rb_hash_new_with_size(RHASH_SIZE(hash));

    rb_hash_foreach(hash, rb_hash_invert_i, h);
    return h;
}


  








  

    

      #keep_if {|key, value| ... } ⇒ self 
      #keep_if  ⇒ Enumerator 
    

  



  

    

Calls the block for each key-value pair; retains the entry if the block returns a truthy value; otherwise deletes the entry; returns self.



h = {foo: 0, bar: 1, baz: 2}
h.keep_if { |key, value| key.start_with?('b') } # => {:bar=>1, :baz=>2}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.keep_if # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:keep_if>
e.each { |key, value| key.start_with?('b') } # => {:bar=>1, :baz=>2}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2813



static VALUE
rb_hash_keep_if(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    if (!RHASH_TABLE_EMPTY_P(hash)) {
        rb_hash_foreach(hash, keep_if_i, hash);
    }
    return hash;
}


  








  

    #key(value)  ⇒ key?   



  

    

Returns the key for the first-found entry with the given value (see Entry Order):



h = {foo: 0, bar: 2, baz: 2}
h.key(0) # => :foo
h.key(2) # => :bar



Returns nil if so such value is found.


  



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# File 'hash.c', line 2298



static VALUE
rb_hash_key(VALUE hash, VALUE value)
{
    VALUE args[2];

    args[0] = value;
    args[1] = Qnil;

    rb_hash_foreach(hash, key_i, (VALUE)args);

    return args[1];
}


  








  

    

      #include?(key)  ⇒ Boolean 
      #has_key?(key)  ⇒ Boolean 
      #key?(key)  ⇒ Boolean 
      #member?(key)  ⇒ Boolean 
    

    Also known as: #include?, #member?, #has_key?
  



  

    

Methods #has_key?, #key?, and #member? are aliases for #include?.



Returns true if #key is a key in self, otherwise false.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3656



MJIT_FUNC_EXPORTED VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
    if (hash_stlike_lookup(hash, key, NULL)) {
        return Qtrue;
    }
    else {
        return Qfalse;
    }
}


  








  

    #keys  ⇒ Array   



  

    

Returns a new Array containing all keys in self:



h = {foo: 0, bar: 1, baz: 2}
h.keys # => [:foo, :bar, :baz]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3567



MJIT_FUNC_EXPORTED VALUE
rb_hash_keys(VALUE hash)
{
    st_index_t size = RHASH_SIZE(hash);
    VALUE keys =  rb_ary_new_capa(size);

    if (size == 0) return keys;

    if (ST_DATA_COMPATIBLE_P(VALUE)) {
        RARRAY_PTR_USE_TRANSIENT(keys, ptr, {
            if (RHASH_AR_TABLE_P(hash)) {
                size = ar_keys(hash, ptr, size);
            }
            else {
                st_table *table = RHASH_ST_TABLE(hash);
                size = st_keys(table, ptr, size);
            }
        });
        rb_gc_writebarrier_remember(keys);
	rb_ary_set_len(keys, size);
    }
    else {
	rb_hash_foreach(hash, keys_i, keys);
    }

    return keys;
}


  








  

    

      #length  ⇒ Integer 
      #size  ⇒ Integer 
    

    Also known as: #size
  



  

    

Returns the count of entries in self:



{foo: 0, bar: 1, baz: 2}.length # => 3



length is an alias for #size.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2999



VALUE
rb_hash_size(VALUE hash)
{
    return INT2FIX(RHASH_SIZE(hash));
}


  








  

    

      #include?(key)  ⇒ Boolean 
      #has_key?(key)  ⇒ Boolean 
      #key?(key)  ⇒ Boolean 
      #member?(key)  ⇒ Boolean 
    

  



  

    

Alias for #key?.


  





  








  

    

      #merge  ⇒ copy_of_self 
      #merge(*other_hashes)  ⇒ Hash 
      #merge(*other_hashes) {|key, old_value, new_value| ... } ⇒ Hash 
    

  



  

    

Returns the new Hash formed by merging each of other_hashes into a copy of self.



Each argument in other_hashes must be a Hash.





With arguments and no block:


  • 

    Returns the new Hash object formed by merging each successive Hash in other_hashes into self.
    

  • 

    Each new-key entry is added at the end.
    

  • 

    Each duplicate-key entry’s value overwrites the previous value.
    




Example:



h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h.merge(h1, h2) # => {:foo=>0, :bar=>4, :baz=>2, :bat=>6, :bam=>5}



With arguments and a block:


  • 

    Returns a new Hash object that is the merge of self and each given hash.
    

  • 

    The given hashes are merged left to right.
    

  • 

    Each new-key entry is added at the end.
    

  • 

    For each duplicate key:
    

    • 

      Calls the block with the key and the old and new values.
      

    • 

      The block’s return value becomes the new value for the entry.
      

    




Example:



h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h3 = h.merge(h1, h2) { |key, old_value, new_value| old_value + new_value }
h3 # => {:foo=>0, :bar=>5, :baz=>2, :bat=>9, :bam=>5}



With no arguments:


  • 

    Returns a copy of self.
    

  • 

    The block, if given, is ignored.
    




Example:



h = {foo: 0, bar: 1, baz: 2}
h.merge # => {:foo=>0, :bar=>1, :baz=>2}
h1 = h.merge { |key, old_value, new_value| raise 'Cannot happen' }
h1 # => {:foo=>0, :bar=>1, :baz=>2}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 4122



static VALUE
rb_hash_merge(int argc, VALUE *argv, VALUE self)
{
    return rb_hash_update(argc, argv, rb_hash_dup(self));
}


  








  

    

      #merge!  ⇒ self 
      #merge!(*other_hashes)  ⇒ self 
      #merge!(*other_hashes) {|key, old_value, new_value| ... } ⇒ self 
    

    Also known as: #update
  



  

    

Merges each of other_hashes into self; returns self.



Each argument in other_hashes must be a Hash.



Method #update is an alias for #merge!.



With arguments and no block:


  • 

    Returns self, after the given hashes are merged into it.
    

  • 

    The given hashes are merged left to right.
    

  • 

    Each new entry is added at the end.
    

  • 

    Each duplicate-key entry’s value overwrites the previous value.
    




Example:



h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h.merge!(h1, h2) # => {:foo=>0, :bar=>4, :baz=>2, :bat=>6, :bam=>5}



With arguments and a block:


  • 

    Returns self, after the given hashes are merged.
    

  • 

    The given hashes are merged left to right.
    

  • 

    Each new-key entry is added at the end.
    

  • 

    For each duplicate key:
    

    • 

      Calls the block with the key and the old and new values.
      

    • 

      The block’s return value becomes the new value for the entry.
      

    




Example:



h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h3 = h.merge!(h1, h2) { |key, old_value, new_value| old_value + new_value }
h3 # => {:foo=>0, :bar=>5, :baz=>2, :bat=>9, :bam=>5}



With no arguments:


  • 

    Returns self, unmodified.
    

  • 

    The block, if given, is ignored.
    




Example:



h = {foo: 0, bar: 1, baz: 2}
h.merge # => {:foo=>0, :bar=>1, :baz=>2}
h1 = h.merge! { |key, old_value, new_value| raise 'Cannot happen' }
h1 # => {:foo=>0, :bar=>1, :baz=>2}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3998



static VALUE
rb_hash_update(int argc, VALUE *argv, VALUE self)
{
    int i;
    bool block_given = rb_block_given_p();

    rb_hash_modify(self);
    for (i = 0; i < argc; i++){
       VALUE hash = to_hash(argv[i]);
       if (block_given) {
           rb_hash_foreach(hash, rb_hash_update_block_i, self);
       }
       else {
           rb_hash_foreach(hash, rb_hash_update_i, self);
       }
    }
    return self;
}


  








  

    #rassoc(value)  ⇒ Array?   



  

    

Returns a new 2-element Array consisting of the key and value of the first-found entry whose value is #== to value (see Entry Order):



h = {foo: 0, bar: 1, baz: 1}
h.rassoc(1) # => [:bar, 1]



Returns nil if no such value found.


  



  [ GitHub ]


  

  


# File 'hash.c', line 4239



VALUE
rb_hash_rassoc(VALUE hash, VALUE obj)
{
    VALUE args[2];

    args[0] = obj;
    args[1] = Qnil;
    rb_hash_foreach(hash, rassoc_i, (VALUE)args);
    return args[1];
}


  








  

    #rehash  ⇒ self   



  

    

Rebuilds the hash table by recomputing the hash index for each key; returns self.



The hash table becomes invalid if the hash value of a key has changed after the entry was created. See Modifying an Active Hash Key.


  



  [ GitHub ]


  

  


# File 'hash.c', line 1978



VALUE
rb_hash_rehash(VALUE hash)
{
    VALUE tmp;
    st_table *tbl;

    if (RHASH_ITER_LEV(hash) > 0) {
	rb_raise(rb_eRuntimeError, "rehash during iteration");
    }
    rb_hash_modify_check(hash);
    if (RHASH_AR_TABLE_P(hash)) {
        tmp = hash_alloc(0);
        ar_alloc_table(tmp);
        rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
        ar_free_and_clear_table(hash);
        ar_copy(hash, tmp);
        ar_free_and_clear_table(tmp);
    }
    else if (RHASH_ST_TABLE_P(hash)) {
        st_table *old_tab = RHASH_ST_TABLE(hash);
        tmp = hash_alloc(0);
        tbl = st_init_table_with_size(old_tab->type, old_tab->num_entries);
        RHASH_ST_TABLE_SET(tmp, tbl);
        rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
        st_free_table(old_tab);
        RHASH_ST_TABLE_SET(hash, tbl);
        RHASH_ST_CLEAR(tmp);
    }
    hash_verify(hash);
    return hash;
}


  








  

    

      #reject {|key, value| ... } ⇒ Hash 
      #reject  ⇒ Enumerator 
    

  



  

    

Returns a new Hash object whose entries are all those from self for which the block returns false or nil:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.reject {|key, value| key.start_with?('b') }
h1 # => {:foo=>0}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.reject # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:reject>
h1 = e.each {|key, value| key.start_with?('b') }
h1 # => {:foo=>0}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2578



VALUE
rb_hash_reject(VALUE hash)
{
    VALUE result;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    if (RTEST(ruby_verbose)) {
	VALUE klass;
	if (HAS_EXTRA_STATES(hash, klass)) {
	    rb_warn("extra states are no longer copied: %+"PRIsVALUE, hash);
	}
    }
    result = rb_hash_new();
    if (!RHASH_EMPTY_P(hash)) {
	rb_hash_foreach(hash, reject_i, result);
    }
    return result;
}


  








  

    

      #reject! {|key, value| ... } ⇒ self? 
      #reject!  ⇒ Enumerator 
    

  



  

    

Returns self, whose remaining entries are those for which the block returns false or nil:



h = {foo: 0, bar: 1, baz: 2}
h.reject! {|key, value| value < 2 } # => {:baz=>2}



Returns nil if no entries are removed.



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.reject! # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:reject!>
e.each {|key, value| key.start_with?('b') } # => {:foo=>0}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2537



VALUE
rb_hash_reject_bang(VALUE hash)
{
    st_index_t n;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify(hash);
    n = RHASH_SIZE(hash);
    if (!n) return Qnil;
    rb_hash_foreach(hash, delete_if_i, hash);
    if (n == RHASH_SIZE(hash)) return Qnil;
    return hash;
}


  








  

    #replace(other_hash)  ⇒ self     Also known as: #initialize_copy
  



  

    

Replaces the entire contents of self with the contents of other_hash; returns self:



h = {foo: 0, bar: 1, baz: 2}
h.replace({bat: 3, bam: 4}) # => {:bat=>3, :bam=>4}


  



  [ GitHub ]


  

  


# File 'hash.c', line 2950



static VALUE
rb_hash_replace(VALUE hash, VALUE hash2)
{
    rb_hash_modify_check(hash);
    if (hash == hash2) return hash;
    if (RHASH_ITER_LEV(hash) > 0) {
        rb_raise(rb_eRuntimeError, "can't replace hash during iteration");
    }
    hash2 = to_hash(hash2);

    COPY_DEFAULT(hash, hash2);

    if (RHASH_AR_TABLE_P(hash)) {
        if (RHASH_AR_TABLE_P(hash2)) {
            ar_clear(hash);
        }
        else {
            ar_free_and_clear_table(hash);
            RHASH_ST_TABLE_SET(hash, st_init_table_with_size(RHASH_TYPE(hash2), RHASH_SIZE(hash2)));
        }
    }
    else {
        if (RHASH_AR_TABLE_P(hash2)) {
            st_free_table(RHASH_ST_TABLE(hash));
            RHASH_ST_CLEAR(hash);
        }
        else {
            st_clear(RHASH_ST_TABLE(hash));
            RHASH_TBL_RAW(hash)->type = RHASH_ST_TABLE(hash2)->type;
        }
    }
    rb_hash_foreach(hash2, rb_hash_rehash_i, (VALUE)hash);

    rb_gc_writebarrier_remember(hash);

    return hash;
}


  








  

    

      #select {|key, value| ... } ⇒ Hash 
      #select  ⇒ Enumerator 
    

  



  

    

Alias for #filter.


  





  








  

    

      #select! {|key, value| ... } ⇒ self? 
      #select!  ⇒ Enumerator 
    

  



  

    

Alias for #filter!.


  





  








  

    #shift  ⇒ Array, value   



  

    

Removes the first hash entry (see Entry Order); returns a 2-element Array containing the removed key and value:



h = {foo: 0, bar: 1, baz: 2}
h.shift # => [:foo, 0]
h # => {:bar=>1, :baz=>2}



Returns the default value if the hash is empty (see Default Values).


  



  [ GitHub ]


  

  


# File 'hash.c', line 2436



static VALUE
rb_hash_shift(VALUE hash)
{
    struct shift_var var;

    rb_hash_modify_check(hash);
    if (RHASH_AR_TABLE_P(hash)) {
	var.key = Qundef;
	if (RHASH_ITER_LEV(hash) == 0) {
            if (ar_shift(hash, &var.key, &var.val)) {
		return rb_assoc_new(var.key, var.val);
	    }
	}
	else {
            rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
            if (var.key != Qundef) {
                rb_hash_delete_entry(hash, var.key);
                return rb_assoc_new(var.key, var.val);
            }
        }
    }
    if (RHASH_ST_TABLE_P(hash)) {
        var.key = Qundef;
        if (RHASH_ITER_LEV(hash) == 0) {
            if (st_shift(RHASH_ST_TABLE(hash), &var.key, &var.val)) {
                return rb_assoc_new(var.key, var.val);
            }
        }
        else {
	    rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
	    if (var.key != Qundef) {
		rb_hash_delete_entry(hash, var.key);
		return rb_assoc_new(var.key, var.val);
	    }
	}
    }
    return rb_hash_default_value(hash, Qnil);
}


  








  

    

      #length  ⇒ Integer 
      #size  ⇒ Integer 
    

  



  

    

Alias for #length.


  





  








  

    #slice(*keys)  ⇒ Hash   



  

    

Returns a new Hash object containing the entries for the given #keys:



h = {foo: 0, bar: 1, baz: 2}
h.slice(:baz, :foo) # => {:baz=>2, :foo=>0}



Any given #keys that are not found are ignored.


  



  [ GitHub ]


  

  


# File 'hash.c', line 2608



static VALUE
rb_hash_slice(int argc, VALUE *argv, VALUE hash)
{
    int i;
    VALUE key, value, result;

    if (argc == 0 || RHASH_EMPTY_P(hash)) {
	return rb_hash_new();
    }
    result = rb_hash_new_with_size(argc);

    for (i = 0; i < argc; i++) {
	key = argv[i];
	value = rb_hash_lookup2(hash, key, Qundef);
	if (value != Qundef)
	    rb_hash_aset(result, key, value);
    }

    return result;
}


  








  

    

      #[]=(key, value)  ⇒ value 
      #store(key, value)  
    

  



  

    

Alias for #[]=.


  





  








  

    #to_a  ⇒ Array   



  

    

Returns a new Array of 2-element Array objects; each nested Array contains a key-value pair from self:



h = {foo: 0, bar: 1, baz: 2}
h.to_a # => [[:foo, 0], [:bar, 1], [:baz, 2]]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3411



static VALUE
rb_hash_to_a(VALUE hash)
{
    VALUE ary;

    ary = rb_ary_new_capa(RHASH_SIZE(hash));
    rb_hash_foreach(hash, to_a_i, ary);

    return ary;
}


  








  

    

      #to_h  ⇒ self, Hash 
      #to_h {|key, value| ... } ⇒ Hash 
    

  



  

    

For an instance of Hash, returns self.



For a subclass of Hash, returns a new Hash containing the content of self.



When a block is given, returns a new Hash object whose content is based on the block; the block should return a 2-element Array object specifying the key-value pair to be included in the returned Array:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.to_h {|key, value| [value, key] }
h1 # => {0=>:foo, 1=>:bar, 2=>:baz}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3538



static VALUE
rb_hash_to_h(VALUE hash)
{
    if (rb_block_given_p()) {
        return rb_hash_to_h_block(hash);
    }
    if (rb_obj_class(hash) != rb_cHash) {
	const VALUE flags = RBASIC(hash)->flags;
        hash = hash_dup(hash, rb_cHash, flags & RHASH_PROC_DEFAULT);
    }
    return hash;
}


  








  

    #to_hash  ⇒ self   



  

    

Returns self.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3480



static VALUE
rb_hash_to_hash(VALUE hash)
{
    return hash;
}


  








  

    #to_proc  ⇒ Proc   



  

    

Returns a Proc object that maps a key to its value:



h = {foo: 0, bar: 1, baz: 2}
proc = h.to_proc
proc.class # => Proc
proc.call(:foo) # => 0
proc.call(:bar) # => 1
proc.call(:nosuch) # => nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 4726



static VALUE
rb_hash_to_proc(VALUE hash)
{
    return rb_func_lambda_new(hash_proc_call, hash, 1, 1);
}


  








  

    #to_s  ⇒ String     Also known as: #inspect
  



  

    

Returns a new String containing the hash entries:



h = {foo: 0, bar: 1, baz: 2}
h.inspect # => "{:foo=>0, :bar=>1, :baz=>2}"



to_s is an alias for #inspect.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3466



static VALUE
rb_hash_inspect(VALUE hash)
{
    if (RHASH_EMPTY_P(hash))
	return rb_usascii_str_new2("{}");
    return rb_exec_recursive(inspect_hash, hash, 0);
}


  








  

    

      #transform_keys {|key| ... } ⇒ Hash 
      #transform_keys(hash2)  ⇒ Hash 
      #transform_keys(hash2) {|other_key| ... } ⇒ Hash 
      #transform_keys  ⇒ Enumerator 
    

  



  

    

Returns a new Hash object; each entry has:


  • 

    A key provided by the block.
    

  • 

    The value from self.
    




An optional hash argument can be provided to map keys to new keys. Any key not given will be mapped using the provided block, or remain the same if no block is given.



Transform keys:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_keys {|key| key.to_s }
h1 # => {"foo"=>0, "bar"=>1, "baz"=>2}

h.transform_keys(foo: :bar, bar: :foo)
#=> {bar: 0, foo: 1, baz: 2}

h.transform_keys(foo: :hello, &:to_s)
#=> {:hello=>0, "bar"=>1, "baz"=>2}



Overwrites values for duplicate keys:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_keys {|key| :bat }
h1 # => {:bat=>2}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.transform_keys # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:transform_keys>
h1 = e.each { |key| key.to_s }
h1 # => {"foo"=>0, "bar"=>1, "baz"=>2}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3226



static VALUE
rb_hash_transform_keys(int argc, VALUE *argv, VALUE hash)
{
    VALUE result;
    struct transform_keys_args transarg = {0};

    argc = rb_check_arity(argc, 0, 1);
    if (argc > 0) {
        transarg.trans = to_hash(argv[0]);
        transarg.block_given = rb_block_given_p();
    }
    else {
        RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    }
    result = rb_hash_new();
    if (!RHASH_EMPTY_P(hash)) {
        if (transarg.trans) {
            transarg.result = result;
            rb_hash_foreach(hash, transform_keys_hash_i, (VALUE)&transarg);
        }
        else {
            rb_hash_foreach(hash, transform_keys_i, result);
        }
    }

    return result;
}


  








  

    

      #transform_keys! {|key| ... } ⇒ self 
      #transform_keys!(hash2)  ⇒ self 
      #transform_keys!(hash2) {|other_key| ... } ⇒ self 
      #transform_keys!  ⇒ Enumerator 
    

  



  

    

Same as #transform_keys but modifies the receiver in place instead of returning a new hash.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3266



static VALUE
rb_hash_transform_keys_bang(int argc, VALUE *argv, VALUE hash)
{
    VALUE trans = 0;
    int block_given = 0;

    argc = rb_check_arity(argc, 0, 1);
    if (argc > 0) {
        trans = to_hash(argv[0]);
        block_given = rb_block_given_p();
    }
    else {
        RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    }
    rb_hash_modify_check(hash);
    if (!RHASH_TABLE_EMPTY_P(hash)) {
        long i;
        VALUE new_keys = hash_alloc(0);
        VALUE pairs = rb_ary_tmp_new(RHASH_SIZE(hash) * 2);
        rb_hash_foreach(hash, flatten_i, pairs);
        for (i = 0; i < RARRAY_LEN(pairs); i += 2) {
            VALUE key = RARRAY_AREF(pairs, i), new_key, val;

            if (!trans) {
                new_key = rb_yield(key);
            }
            else if ((new_key = rb_hash_lookup2(trans, key, Qundef)) != Qundef) {
                /* use the transformed key */
            }
            else if (block_given) {
                new_key = rb_yield(key);
            }
            else {
                new_key = key;
            }
            val = RARRAY_AREF(pairs, i+1);
            if (!hash_stlike_lookup(new_keys, key, NULL)) {
                rb_hash_stlike_delete(hash, &key, NULL);
            }
            rb_hash_aset(hash, new_key, val);
            rb_hash_aset(new_keys, new_key, Qnil);
        }
        rb_ary_clear(pairs);
        rb_hash_clear(new_keys);
    }
    return hash;
}


  








  

    

      #transform_values {|value| ... } ⇒ Hash 
      #transform_values  ⇒ Enumerator 
    

  



  

    

Returns a new Hash object; each entry has:


  • 

    A key from self.
    

  • 

    A value provided by the block.
    




Transform values:



h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_values {|value| value * 100}
h1 # => {:foo=>0, :bar=>100, :baz=>200}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.transform_values # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:transform_values>
h1 = e.each { |value| value * 100}
h1 # => {:foo=>0, :bar=>100, :baz=>200}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3350



static VALUE
rb_hash_transform_values(VALUE hash)
{
    VALUE result;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    result = hash_copy(hash_alloc(rb_cHash), hash);
    SET_DEFAULT(result, Qnil);

    if (!RHASH_EMPTY_P(hash)) {
        rb_hash_stlike_foreach_with_replace(result, transform_values_foreach_func, transform_values_foreach_replace, result);
    }

    return result;
}


  








  

    

      #transform_values! {|value| ... } ⇒ self 
      #transform_values!  ⇒ Enumerator 
    

  



  

    

Returns self, whose keys are unchanged, and whose values are determined by the given block.



h = {foo: 0, bar: 1, baz: 2}
h.transform_values! {|value| value * 100} # => {:foo=>0, :bar=>100, :baz=>200}



Returns a new Enumerator if no block given:



h = {foo: 0, bar: 1, baz: 2}
e = h.transform_values! # => #<Enumerator: {:foo=>0, :bar=>100, :baz=>200}:transform_values!>
h1 = e.each {|value| value * 100}
h1 # => {:foo=>0, :bar=>100, :baz=>200}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3381



static VALUE
rb_hash_transform_values_bang(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);

    if (!RHASH_TABLE_EMPTY_P(hash)) {
        rb_hash_stlike_foreach_with_replace(hash, transform_values_foreach_func, transform_values_foreach_replace, hash);
    }

    return hash;
}


  








  

    

      #merge!  ⇒ self 
      #merge!(*other_hashes)  ⇒ self 
      #merge!(*other_hashes) {|key, old_value, new_value| ... } ⇒ self 
    

  



  

    

Alias for #merge!.


  





  








  

    #value?(value)  ⇒ Boolean     Also known as: #has_value?
  



  

    

Returns true if value is a value in self, otherwise false.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3686



static VALUE
rb_hash_has_value(VALUE hash, VALUE val)
{
    VALUE data[2];

    data[0] = Qfalse;
    data[1] = val;
    rb_hash_foreach(hash, rb_hash_search_value, (VALUE)data);
    return data[0];
}


  








  

    #values  ⇒ Array   



  

    

Returns a new Array containing all values in self:



h = {foo: 0, bar: 1, baz: 2}
h.values # => [0, 1, 2]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3611



VALUE
rb_hash_values(VALUE hash)
{
    VALUE values;
    st_index_t size = RHASH_SIZE(hash);

    values = rb_ary_new_capa(size);
    if (size == 0) return values;

    if (ST_DATA_COMPATIBLE_P(VALUE)) {
        if (RHASH_AR_TABLE_P(hash)) {
            rb_gc_writebarrier_remember(values);
            RARRAY_PTR_USE_TRANSIENT(values, ptr, {
                size = ar_values(hash, ptr, size);
            });
        }
        else if (RHASH_ST_TABLE_P(hash)) {
            st_table *table = RHASH_ST_TABLE(hash);
            rb_gc_writebarrier_remember(values);
            RARRAY_PTR_USE_TRANSIENT(values, ptr, {
                size = st_values(table, ptr, size);
            });
        }
	rb_ary_set_len(values, size);
    }

    else {
	rb_hash_foreach(hash, values_i, values);
    }

    return values;
}


  








  

    #values_at(*keys)  ⇒ Array   



  

    

Returns a new Array containing values for the given #keys:



h = {foo: 0, bar: 1, baz: 2}
h.values_at(:baz, :foo) # => [2, 0]



The default values are returned for any keys that are not found:



h.values_at(:hello, :foo) # => [nil, 0]


  



  [ GitHub ]


  

  


# File 'hash.c', line 2670



VALUE
rb_hash_values_at(int argc, VALUE *argv, VALUE hash)
{
    VALUE result = rb_ary_new2(argc);
    long i;

    for (i=0; i<argc; i++) {
	rb_ary_push(result, rb_hash_aref(hash, argv[i]));
    }
    return result;
}