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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 is a dictionary-like collection of unique keys and their values. Also called associative arrays, they are similar to Arrays, but where an ::Array uses integers as its index, a Hash allows you to use any object type.

Hashes enumerate their values in the order that the corresponding keys were inserted.

A Hash can be easily created by using its implicit form:

grades = { "Jane Doe" => 10, "Jim Doe" => 6 }

Hashes allow an alternate syntax for keys that are symbols. Instead of

options = { :font_size => 10, :font_family => "Arial" }

You could write it as:

options = { font_size: 10, font_family: "Arial" }

Each named key is a symbol you can access in hash:

options[:font_size]  # => 10

A Hash can also be created through its .new method:

grades = Hash.new
grades["Dorothy Doe"] = 9

Hashes have a default value that is returned when accessing keys that do not exist in the hash. If no default is set nil is used. You can set the default value by sending it as an argument to .new:

grades = Hash.new(0)

Or by using the #default= method:

grades = {"Timmy Doe" => 8}
grades.default = 0

Accessing a value in a Hash requires using its key:

puts grades["Jane Doe"] # => 0

Common Uses

Hashes are an easy way to represent data structures, such as

books         = {}
books[:matz]  = "The Ruby Programming Language"
books[:black] = "The Well-Grounded Rubyist"

Hashes are also commonly used as a way to have named parameters in functions. Note that no brackets are used below. If a hash is the last argument on a method call, no braces are needed, thus creating a really clean interface:

Person.create(name: "John Doe", age: 27)

def self.create(params)
  @name = params[:name]
  @age  = params[:age]
end

Hash Keys

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

A user-defined class may be used as a hash key if the #hash and #eql? methods are overridden to provide meaningful behavior. By default, separate instances refer to separate hash keys.

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 and
      other.author == @author and
      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

See also Object#hash and Object#eql?

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 ⇒ Hash .new(obj) ⇒ Hash .new {|hash, key| ... } ⇒ Hash

Returns a new, empty hash. If this hash is subsequently accessed by a key that doesn’t correspond to a hash entry, the value returned depends on the style of new used to create the hash. In the first form, the access returns nil. If obj is specified, this single object will be used for all default values. If a block is specified, it will be called with the hash object and the key, and should return the default value. It is the block’s responsibility to store the value in the hash if required.

h = Hash.new("Go Fish")
h["a"] = 100
h["b"] = 200
h["a"]           #=> 100
h["c"]           #=> "Go Fish"
# The following alters the single default object
h["c"].upcase!   #=> "GO FISH"
h["d"]           #=> "GO FISH"
h.keys           #=> ["a", "b"]

# While this creates a new default object each time
h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" }
h["c"]           #=> "Go Fish: c"
h["c"].upcase!   #=> "GO FISH: C"
h["d"]           #=> "Go Fish: d"
h.keys           #=> ["c", "d"]
[ GitHub ] 

  


# File 'hash.c', line 1764



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



  

    

      .[](key, value, ... )  ⇒ Hash 
      .[]([ [key, value], ... ] )  ⇒ Hash 
      .[](object )  ⇒ Hash 
    

  



  

    

Creates a new hash populated with the given objects.



Similar to the literal { key => value, ... }. In the first form, keys and values occur in pairs, so there must be an even number of arguments.



The second and third form take a single argument which is either an array of key-value pairs or an object convertible to a hash.



Hash["a", 100, "b", 200]             #=> {"a"=>100, "b"=>200}
Hash[ [ ["a", 100], ["b", 200] ] ]   #=> {"a"=>100, "b"=>200}
Hash["a" => 100, "b" => 200]         #=> {"a"=>100, "b"=>200}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 1804



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);
            if (RHASH_AR_TABLE_P(tmp)) {
                ar_copy(hash, tmp);
	    }
            else {
                RHASH_ST_TABLE_SET(hash, st_copy(RHASH_ST_TABLE(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 1927



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 1905



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)  ⇒ Hash?   



  

    

Try to convert obj into a hash, using to_hash method. Returns converted hash or nil if obj cannot be converted for any reason.



Hash.try_convert({1=>2})   # => {1=>2}
Hash.try_convert("1=>2")   # => nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 1884



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


  







Instance Attribute Details



  

    #compare_by_identity  ⇒ Hash  (readonly)  



  

    

Makes hsh compare its keys by their identity, i.e. it will consider exact same objects as same keys.



h1 = { "a" => 100, "b" => 200, :c => "c" }
h1["a"]        #=> 100
h1.compare_by_identity
h1.compare_by_identity? #=> true
h1["a".dup]    #=> nil  # different objects.
h1[:c]         #=> "c"  # same symbols are all same.


  



  [ GitHub ]


  

  


# File 'hash.c', line 4249



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 hsh will compare its keys by their identity.  Also see #compare_by_identity.


  



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# File 'hash.c', line 4282



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  ⇒ Object  (rw)  



  

    

If .new was invoked with a block, return that block, otherwise return nil.



h = Hash.new {|h,k| h[k] = k*k }   #=> {}
p = h.default_proc                 #=> #<Proc:0x401b3d08@-:1>
a = []                             #=> []
p.call(a, 2)
a                                  #=> [nil, nil, 4]


  



  [ GitHub ]


  

  


# File 'hash.c', line 2235



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


  








  

    #default_proc=(proc_obj or nil)   (rw)  



  

    

Sets the default proc to be executed on each failed key lookup.



h.default_proc = proc do |hash, key|
  hash[key] = key + key
end
h[2]       #=> 4
h["cat"]   #=> "catcat"


  



  [ GitHub ]


  

  


# File 'hash.c', line 2257



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 hsh contains no key-value pairs.



{}.empty?   #=> true


  



  [ GitHub ]


  

  


# File 'hash.c', line 2976



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


  







Instance Method Details



  

    #<(other)  ⇒ Boolean   



  

    

Returns true if hash is subset of other.



h1 = {a:1, b:2}
h2 = {a:1, b:2, c:3}
h1 < h2    #=> true
h2 < h1    #=> false
h1 < h1    #=> false


  



  [ GitHub ]


  

  


# File 'hash.c', line 4466



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)  ⇒ Boolean   



  

    

Returns true if hash is subset of other or equals to other.



h1 = {a:1, b:2}
h2 = {a:1, b:2, c:3}
h1 <= h2   #=> true
h2 <= h1   #=> false
h1 <= h1   #=> true


  



  [ GitHub ]


  

  


# File 'hash.c', line 4445



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);
}


  








  

    #==(other_hash)  ⇒ Boolean   



  

    

Equality—Two hashes are equal if they each contain the same number of keys and if each key-value pair is equal to (according to Object#==) the corresponding elements in the other hash.



h1 = { "a" => 1, "c" => 2 }
h2 = { 7 => 35, "c" => 2, "a" => 1 }
h3 = { "a" => 1, "c" => 2, 7 => 35 }
h4 = { "a" => 1, "d" => 2, "f" => 35 }
h1 == h2   #=> false
h2 == h3   #=> true
h3 == h4   #=> false



The orders of each hashes are not compared.



h1 = { "a" => 1, "c" => 2 }
h2 = { "c" => 2, "a" => 1 }
h1 == h2   #=> true


  



  [ GitHub ]


  

  


# File 'hash.c', line 3674



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


  








  

    #>(other)  ⇒ Boolean   



  

    

Returns true if other is subset of hash.



h1 = {a:1, b:2}
h2 = {a:1, b:2, c:3}
h1 > h2    #=> false
h2 > h1    #=> true
h1 > h1    #=> false


  



  [ GitHub ]


  

  


# File 'hash.c', line 4508



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)  ⇒ Boolean   



  

    

Returns true if other is subset of hash or equals to hash.



h1 = {a:1, b:2}
h2 = {a:1, b:2, c:3}
h1 >= h2   #=> false
h2 >= h1   #=> true
h1 >= h1   #=> true


  



  [ GitHub ]


  

  


# File 'hash.c', line 4487



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   



  

    

Element Reference—Retrieves the value object corresponding to the key object. If not found, returns the default value (see .new for details).



h = { "a" => 100, "b" => 200 }
h["a"]   #=> 100
h["c"]   #=> nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 2052



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)  ⇒ value 
    

    Also known as: #store
  



  

    

Element Assignment



Associates the value given by value with the key given by #key.



h = { "a" => 100, "b" => 200 }
h["a"] = 9
h["c"] = 4
h   #=> {"a"=>9, "b"=>200, "c"=>4}
h.store("d", 42) #=> 42
h   #=> {"a"=>9, "b"=>200, "c"=>4, "d"=>42}



#key should not have its value changed while it is in use as a key (an unfrozen String passed as a key will be duplicated and frozen).



a = "a"
b = "b".freeze
h = { a => 100, b => 200 }
h.key(100).equal? a #=> false
h.key(200).equal? b #=> true


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2867



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

  



  

    

See also Enumerable#any?


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 4354



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_arity() > 1)
	    rb_hash_foreach(hash, any_p_i_fast, (VALUE)args);
	else
	    rb_hash_foreach(hash, any_p_i, (VALUE)args);
    }
    return args[0];
}


  








  

    #assoc(obj)  ⇒ Array?   



  

    

Searches through the hash comparing obj with the key using #==. Returns the key-value pair (two elements array) or nil if no match is found.  See Array#assoc.



h = {"colors"  => ["red", "blue", "green"],
     "letters" => ["a", "b", "c" ]}
h.assoc("letters")  #=> ["letters", ["a", "b", "c"]]
h.assoc("foo")      #=> nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 4032



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  ⇒ Hash   



  

    

Removes all key-value pairs from hsh.



h = { "a" => 100, "b" => 200 }   #=> {"a"=>100, "b"=>200}
h.clear                          #=> {}


  



  [ GitHub ]


  

  


# File 'hash.c', line 2784



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 new hash with the nil values/key pairs removed



h = { a: 1, b: false, c: nil }
h.compact     #=> { a: 1, b: false }
h             #=> { a: 1, b: false, c: nil }


  



  [ GitHub ]


  

  


# File 'hash.c', line 4195



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!  ⇒ Hash?   



  

    

Removes all nil values from the hash. Returns nil if no changes were made, otherwise returns the hash.



h = { a: 1, b: false, c: nil }
h.compact!     #=> { a: 1, b: false }


  



  [ GitHub ]


  

  


# File 'hash.c', line 4217



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 4542



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


  








  

    #default(key = nil)  ⇒ Object   



  

    

Returns the default value, the value that would be returned by hsh[key] if key did not exist in hsh. See also .new and #default=.



h = Hash.new                            #=> {}
h.default                               #=> nil
h.default(2)                            #=> nil

h = Hash.new("cat")                     #=> {}
h.default                               #=> "cat"
h.default(2)                            #=> "cat"

h = Hash.new {|h,k| h[k] = k.to_i*10}   #=> {}
h.default                               #=> nil
h.default(2)                            #=> 20


  



  [ GitHub ]


  

  


# File 'hash.c', line 2176



static VALUE
rb_hash_default(int argc, VALUE *argv, VALUE hash)
{
    VALUE args[2], ifnone;

    rb_check_arity(argc, 0, 1);
    ifnone = RHASH_IFNONE(hash);
    if (FL_TEST(hash, RHASH_PROC_DEFAULT)) {
	if (argc == 0) return Qnil;
	args[0] = hash;
	args[1] = argv[0];
	return rb_funcallv(ifnone, id_yield, 2, args);
    }
    return ifnone;
}


  








  

    #default=(obj)  ⇒ Object   



  

    

Sets the default value, the value returned for a key that does not exist in the hash. It is not possible to set the default to a ::Proc that will be executed on each key lookup.



h = { "a" => 100, "b" => 200 }
h.default = "Go fish"
h["a"]     #=> 100
h["z"]     #=> "Go fish"
# This doesn't do what you might hope...
h.default = proc do |hash, key|
  hash[key] = key + key
end
h[2]       #=> #<Proc:0x401b3948@-:6>
h["cat"]   #=> #<Proc:0x401b3948@-:6>


  



  [ GitHub ]


  

  


# File 'hash.c', line 2212



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| ... } ⇒ value 
    

  



  

    

Deletes the key-value pair and returns the value from hsh whose key is equal to key. If the key is not found, it returns nil. If the optional code block is given and the key is not found, pass in the key and return the result of block.



h = { "a" => 100, "b" => 200 }
h.delete("a")                              #=> 100
h.delete("z")                              #=> nil
h.delete("z") { |el| "#{el} not found" }   #=> "z not found"


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2390



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| ... } ⇒ Hash 
      #delete_if  ⇒ Enumerator 
    

  



  

    

Deletes every key-value pair from hsh for which block evaluates to true.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200, "c" => 300 }
h.delete_if {|key, value| key >= "b" }   #=> {"a"=>100}


  





  


  [ 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, ...)  ⇒ Object   



  

    

Extracts the nested value specified by the sequence of key objects by calling dig at each step, returning nil if any intermediate step is nil.



h = { foo: {bar: {baz: 1}}}

h.dig(:foo, :bar, :baz)     #=> 1
h.dig(:foo, :zot, :xyz)     #=> nil

g = { foo: [10, 11, 12] }
g.dig(:foo, 1)              #=> 11
g.dig(:foo, 1, 0)           #=> TypeError: Integer does not have #dig method
g.dig(:foo, :bar)           #=> TypeError: no implicit conversion of Symbol into Integer


  



  [ GitHub ]


  

  


# File 'hash.c', line 4402



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

    Also known as: #each_pair
  



  

    

Calls block once for each key in hsh, passing the key-value pair as parameters.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200 }
h.each {|key, value| puts "#{key} is #{value}" }



produces:



a is 100
b is 200


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3088



static VALUE
rb_hash_each_pair(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    if (rb_block_arity() > 1)
	rb_hash_foreach(hash, each_pair_i_fast, 0);
    else
	rb_hash_foreach(hash, each_pair_i, 0);
    return hash;
}


  








  

    

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

  



  

    

Calls block once for each key in hsh, passing the key as a parameter.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200 }
h.each_key {|key| puts key }



produces:



a
b


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3041



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

  



  

    

Alias for #each.


  





  








  

    

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

  



  

    

Calls block once for each key in hsh, passing the value as a parameter.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200 }
h.each_value {|value| puts value }



produces:



100
200


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3008



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?(other)  ⇒ Boolean   



  

    

Returns true if hash and other are both hashes with the same content. The orders of each hashes are not compared.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3689



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


  








  

    

      #fetch(key [, default] )  ⇒ Object 
      #fetch(key) {|key| ... } ⇒ Object 
    

  



  

    

Returns a value from the hash for the given key. If the key can’t be found, there are several options: With no other arguments, it will raise a ::KeyError exception; if default is given, then that will be returned; if the optional code block is specified, then that will be run and its result returned.



h = { "a" => 100, "b" => 200 }
h.fetch("a")                            #=> 100
h.fetch("z", "go fish")                 #=> "go fish"
h.fetch("z") { |el| "go fish, #{el}"}   #=> "go fish, z"



The following example shows that an exception is raised if the key is not found and a default value is not supplied.



h = { "a" => 100, "b" => 200 }
h.fetch("z")



produces:



prog.rb:2:in `fetch': key not found (KeyError)
 from prog.rb:2


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2113



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(key, ...)  ⇒ Array 
      #fetch_values(key, ...) {|key| ... } ⇒ Array 
    

  



  

    

Returns an array containing the values associated with the given keys but also raises ::KeyError when one of keys can’t be found. Also see #values_at and #fetch.



h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }

h.fetch_values("cow", "cat")                   #=> ["bovine", "feline"]
h.fetch_values("cow", "bird")                  # raises KeyError
h.fetch_values("cow", "bird") { |k| k.upcase } #=> ["bovine", "BIRD"]


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2655



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

    Also known as: #select
  



  

    

Returns a new hash consisting of entries for which the block returns true.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200, "c" => 300 }
h.select {|k,v| k > "a"}  #=> {"b" => 200, "c" => 300}
h.select {|k,v| v < 200}  #=> {"a" => 100}



filter is an alias for #select.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2694



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

    Also known as: #select!
  



  

    

Equivalent to #keep_if, but returns nil if no changes were made.



filter! is an alias for #select!.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2729



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 that is a one-dimensional flattening of this hash. That is, for every key or value that is an array, extract its elements into the new array.  Unlike Array#flatten, this method does not flatten recursively by default.  The optional level argument determines the level of recursion to flatten.



a =  {1=> "one", 2 => [2,"two"], 3 => "three"}
a.flatten    # => [1, "one", 2, [2, "two"], 3, "three"]
a.flatten(2) # => [1, "one", 2, 2, "two", 3, "three"]


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 4132



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;
}


  








  

    

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

  



  

    

Alias for #key?.


  





  








  

    

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

  



  

    

Alias for #value?.


  





  








  

    #hash  ⇒ Integer   



  

    

Compute a hash-code for this hash. Two hashes with the same content will have the same hash code (and will compare using #eql?).



See also Object#hash.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3717



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);
}


  








  

    

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

  



  

    

Alias for #key?.


  





  








  

    #index(value)  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'hash.c', line 2318



static VALUE
rb_hash_index(VALUE hash, VALUE value)
{
    rb_warn_deprecated("Hash#index", "Hash#key");
    return rb_hash_key(hash, value);
}


  








  

    

      #replace(other_hash)  ⇒ Hash 
      #initialize_copy(other_hash)  ⇒ Hash 
    

  



  

    

Alias for #replace.


  





  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

  



  

    

Alias for #to_s.


  





  








  

    #invert  ⇒ Hash   



  

    

Returns a new hash created by using hsh’s values as keys, and the keys as values. If a key with the same value already exists in the hsh, then the last one defined will be used, the earlier value(s) will be discarded.



h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 }
h.invert   #=> {0=>"a", 100=>"m", 200=>"d", 300=>"y"}



If there is no key with the same value, invert is involutive.



h = { a: 1, b: 3, c: 4 }
h.invert.invert == h #=> true



The condition, no key with the same value, can be tested by comparing the size of inverted hash.



# no key with the same value
h = { a: 1, b: 3, c: 4 }
h.size == h.invert.size #=> true

# two (or more) keys has the same value
h = { a: 1, b: 3, c: 1 }
h.size == h.invert.size #=> false


  



  [ GitHub ]


  

  


# File 'hash.c', line 3767



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| ... } ⇒ Hash 
      #keep_if  ⇒ Enumerator 
    

  



  

    

Deletes every key-value pair from hsh for which block evaluates to false.



If no block is given, an enumerator is returned instead.



See also #select!.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2756



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 of an occurrence of a given value. If the value is not found, returns nil.



h = { "a" => 100, "b" => 200, "c" => 300, "d" => 300 }
h.key(200)   #=> "b"
h.key(300)   #=> "c"
h.key(999)   #=> nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 2304



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];
}


  








  

    

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

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



  

    

Returns true if the given key is present in hsh.



h = { "a" => 100, "b" => 200 }
h.has_key?("a")   #=> true
h.has_key?("z")   #=> false



Note that #include? and #member? do not test member equality using #== as do other Enumerables.



See also Enumerable#include?


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3522



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 populated with the keys from this hash. See also #values.



h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 }
h.keys   #=> ["a", "b", "c", "d"]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3424



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 number of key-value pairs in the hash.



h = { "d" => 100, "a" => 200, "v" => 300, "e" => 400 }
h.size          #=> 4
h.delete("a")   #=> 200
h.size          #=> 3
h.length        #=> 3



length is an alias for #size.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2954



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


  








  

    

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

  



  

    

Alias for #key?.


  





  








  

    

      #merge(other_hash1, other_hash2, ...)  ⇒ Hash 
      #merge(other_hash1, other_hash2, ...) {|key, oldval, newval| ... } 
      #-  
    

  



  

    

Returns a new hash that combines the contents of the receiver and the contents of the given hashes.



If no block is given, entries with duplicate keys are overwritten with the values from each other_hash successively, otherwise the value for each duplicate key is determined by calling the block with the key, its value in the receiver and its value in each other_hash.



When called without any argument, returns a copy of the receiver.



h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 246, "c" => 300 }
h3 = { "b" => 357, "d" => 400 }
h1.merge          #=> {"a"=>100, "b"=>200}
h1.merge(h2)      #=> {"a"=>100, "b"=>246, "c"=>300}
h1.merge(h2, h3)  #=> {"a"=>100, "b"=>357, "c"=>300, "d"=>400}
h1.merge(h2) {|key, oldval, newval| newval - oldval}
                  #=> {"a"=>100, "b"=>46,  "c"=>300}
h1.merge(h2, h3) {|key, oldval, newval| newval - oldval}
                  #=> {"a"=>100, "b"=>311, "c"=>300, "d"=>400}
h1                #=> {"a"=>100, "b"=>200}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3973



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


  








  

    

      #merge!(other_hash1, other_hash2, ...)  ⇒ Hash 
      #update(other_hash1, other_hash2, ...)  ⇒ Hash 
      #merge!(other_hash1, other_hash2, ...) {|key, oldval, newval| ... } 
      #-  
      #update(other_hash1, other_hash2, ...) {|key, oldval, newval| ... } 
      #-  
    

    Also known as: #update
  



  

    

Adds the contents of the given hashes to the receiver.



If no block is given, entries with duplicate keys are overwritten with the values from each other_hash successively, otherwise the value for each duplicate key is determined by calling the block with the key, its value in the receiver and its value in each other_hash.



h1 = { "a" => 100, "b" => 200 }
h1.merge!          #=> {"a"=>100, "b"=>200}
h1                 #=> {"a"=>100, "b"=>200}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 246, "c" => 300 }
h1.merge!(h2)      #=> {"a"=>100, "b"=>246, "c"=>300}
h1                 #=> {"a"=>100, "b"=>246, "c"=>300}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 246, "c" => 300 }
h3 = { "b" => 357, "d" => 400 }
h1.merge!(h2, h3)
                   #=> {"a"=>100, "b"=>357, "c"=>300, "d"=>400}
h1                 #=> {"a"=>100, "b"=>357, "c"=>300, "d"=>400}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 246, "c" => 300 }
h3 = { "b" => 357, "d" => 400 }
h1.merge!(h2, h3) {|key, v1, v2| v1 }
                   #=> {"a"=>100, "b"=>200, "c"=>300, "d"=>400}
h1                 #=> {"a"=>100, "b"=>200, "c"=>300, "d"=>400}



#update is an alias for merge!.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3869



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(obj)  ⇒ Array?   



  

    

Searches through the hash comparing obj with the value using #==. Returns the first key-value pair (two-element array) that matches. See also Array#rassoc.



a = {1=> "one", 2 => "two", 3 => "three", "ii" => "two"}
a.rassoc("two")    #=> [2, "two"]
a.rassoc("four")   #=> nil


  



  [ GitHub ]


  

  


# File 'hash.c', line 4093



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  ⇒ Hash   



  

    

Rebuilds the hash based on the current hash values for each key. If values of key objects have changed since they were inserted, this method will reindex hsh. If rehash is called while an iterator is traversing the hash, a ::RuntimeError will be raised in the iterator.



a = [ "a", "b" ]
c = [ "c", "d" ]
h = { a => 100, c => 300 }
h[a]       #=> 100
a[0] = "z"
h[a]       #=> nil
h.rehash   #=> {["z", "b"]=>100, ["c", "d"]=>300}
h[a]       #=> 100


  



  [ GitHub ]


  

  


# File 'hash.c', line 1973



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 consisting of entries for which the block returns false.



If no block is given, an enumerator is returned instead.



h = { "a" => 100, "b" => 200, "c" => 300 }
h.reject {|k,v| k < "b"}  #=> {"b" => 200, "c" => 300}
h.reject {|k,v| v > 100}  #=> {"a" => 100}


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2565



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| ... } ⇒ Hash? 
      #reject!  ⇒ Enumerator 
    

  



  

    

Equivalent to #delete_if, but returns nil if no changes were made.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 2528



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)  ⇒ Hash     Also known as: #initialize_copy
  



  

    

Replaces the contents of hsh with the contents of other_hash.



h = { "a" => 100, "b" => 200 }
h.replace({ "c" => 300, "d" => 400 })   #=> {"c"=>300, "d"=>400}


  



  [ GitHub ]


  

  


# File 'hash.c', line 2900



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

  



  

    

Alias for #filter.


  





  








  

    

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

  



  

    

Alias for #filter!.


  





  








  

    #shift  ⇒ Array, Object   



  

    

Removes a key-value pair from hsh and returns it as the two-item array [ key, value ], or the hash’s default value if the hash is empty.



h = { 1 => "a", 2 => "b", 3 => "c" }
h.shift   #=> [1, "a"]
h         #=> {2=>"b", 3=>"c"}


  



  [ GitHub ]


  

  


# File 'hash.c', line 2439



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 hash containing only the given keys and their values.



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


  



  [ GitHub ]


  

  


# File 'hash.c', line 2595



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)  ⇒ value 
    

  



  

    

Alias for #[]=.


  





  








  

    #to_a  ⇒ Array   



  

    

Converts hsh to a nested array of [ key, value ] arrays.



h = { "c" => 300, "a" => 100, "d" => 400, "c" => 300  }
h.to_a   #=> [["c", 300], ["a", 100], ["d", 400]]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3271



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

  



  

    

Returns self. If called on a subclass of Hash, converts the receiver to a Hash object.



If a block is given, the results of the block on each pair of the receiver will be used as pairs.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3392



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  ⇒ Hash   



  

    

Returns self.


  



  [ GitHub ]


  

  


# File 'hash.c', line 3341



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


  








  

    #to_proc  ⇒ Proc   



  

    

Returns a ::Proc which maps keys to values.



h = {a:1, b:2}
hp = h.to_proc
hp.call(:a)          #=> 1
hp.call(:b)          #=> 2
hp.call(:c)          #=> nil
[:a, :b, :c].map(&h) #=> [1, 2, nil]


  



  [ GitHub ]


  

  


# File 'hash.c', line 4536



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


  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

    Also known as: #inspect
  



  

    

Return the contents of this hash as a string.



h = { "c" => 300, "a" => 100, "d" => 400, "c" => 300  }
h.to_s   #=> "{\"c\"=>300, \"a\"=>100, \"d\"=>400}"


  



  [ GitHub ]


  

  


# File 'hash.c', line 3326



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  ⇒ Enumerator 
    

  



  

    

Returns a new hash with the results of running the block once for every key. This method does not change the values.



h = { a: 1, b: 2, c: 3 }
h.transform_keys {|k| k.to_s }  #=> { "a" => 1, "b" => 2, "c" => 3 }
h.transform_keys(&:to_s)        #=> { "a" => 1, "b" => 2, "c" => 3 }
h.transform_keys.with_index {|k, i| "#{k}.#{i}" }
                                #=> { "a.0" => 1, "b.1" => 2, "c.2" => 3 }



If no block is given, an enumerator is returned instead.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3124



static VALUE
rb_hash_transform_keys(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, transform_keys_i, result);
    }

    return result;
}


  








  

    

      #transform_keys! {|key| ... } ⇒ Hash 
      #transform_keys!  ⇒ Enumerator 
    

  



  

    

Invokes the given block once for each key in hsh, replacing it with the new key returned by the block, and then returns hsh. This method does not change the values.



h = { a: 1, b: 2, c: 3 }
h.transform_keys! {|k| k.to_s }  #=> { "a" => 1, "b" => 2, "c" => 3 }
h.transform_keys!(&:to_sym)      #=> { a: 1, b: 2, c: 3 }
h.transform_keys!.with_index {|k, i| "#{k}.#{i}" }
                                 #=> { "a.0" => 1, "b.1" => 2, "c.2" => 3 }



If no block is given, an enumerator is returned instead.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3157



static VALUE
rb_hash_transform_keys_bang(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    if (!RHASH_TABLE_EMPTY_P(hash)) {
        long i;
        VALUE pairs = rb_hash_flatten(0, NULL, hash);
        rb_hash_clear(hash);
        for (i = 0; i < RARRAY_LEN(pairs); i += 2) {
            VALUE key = RARRAY_AREF(pairs, i), new_key = rb_yield(key),
                  val = RARRAY_AREF(pairs, i+1);
            rb_hash_aset(hash, new_key, val);
        }
    }
    return hash;
}


  








  

    

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

  



  

    

Returns a new hash with the results of running the block once for every value. This method does not change the keys.



h = { a: 1, b: 2, c: 3 }
h.transform_values {|v| v * v + 1 }  #=> { a: 2, b: 5, c: 10 }
h.transform_values(&:to_s)           #=> { a: "1", b: "2", c: "3" }
h.transform_values.with_index {|v, i| "#{v}.#{i}" }
                                     #=> { a: "1.0", b: "2.1", c: "3.2" }



If no block is given, an enumerator is returned instead.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3207



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| ... } ⇒ Hash 
      #transform_values!  ⇒ Enumerator 
    

  



  

    

Invokes the given block once for each value in hsh, replacing it with the new value returned by the block, and then returns hsh. This method does not change the keys.



h = { a: 1, b: 2, c: 3 }
h.transform_values! {|v| v * v + 1 }  #=> { a: 2, b: 5, c: 10 }
h.transform_values!(&:to_s)           #=> { a: "2", b: "5", c: "10" }
h.transform_values!.with_index {|v, i| "#{v}.#{i}" }
                                      #=> { a: "2.0", b: "5.1", c: "10.2" }



If no block is given, an enumerator is returned instead.


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3240



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!(other_hash1, other_hash2, ...)  ⇒ Hash 
      #update(other_hash1, other_hash2, ...)  ⇒ Hash 
      #merge!(other_hash1, other_hash2, ...) {|key, oldval, newval| ... } 
      #-  
      #update(other_hash1, other_hash2, ...) {|key, oldval, newval| ... } 
      #-  
    

  



  

    

Alias for #merge!.


  





  








  

    

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

    Also known as: #has_value?
  



  

    

Returns true if the given value is present for some key in hsh.



h = { "a" => 100, "b" => 200 }
h.value?(100)   #=> true
h.value?(999)   #=> false


  





  


  [ GitHub ]


  

  


# File 'hash.c', line 3558



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 populated with the values from hsh. See also #keys.



h = { "a" => 100, "b" => 200, "c" => 300 }
h.values   #=> [100, 200, 300]


  



  [ GitHub ]


  

  


# File 'hash.c', line 3471



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(key, ...)  ⇒ Array   



  

    

Return an array containing the values associated with the given keys. Also see #select.



h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }
h.values_at("cow", "cat")  #=> ["bovine", "feline"]


  



  [ GitHub ]


  

  


# File 'hash.c', line 2627



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;
}