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

Class Method Summary

.[](key, value, ... ) ⇒ Hash

Creates a new hash populated with the given objects.
.new ⇒ Hash constructor

Returns a new, empty hash.
.try_convert(obj) ⇒ Hash^?

Try to convert obj into a hash, using to_hash method.

Instance Attribute Summary

#compare_by_identity ⇒ Hash readonly

Makes hsh compare its keys by their identity, i.e. it will consider exact same objects as same keys.
#compare_by_identity? ⇒ Boolean readonly

Returns true if hsh will compare its keys by their identity.
#default_proc ⇒ Object rw

If .new was invoked with a block, return that block, otherwise return nil.
#default_proc=(proc_obj or nil) rw

Sets the default proc to be executed on each failed key lookup.
#empty? ⇒ Boolean readonly

Returns true if hsh contains no key-value pairs.

Instance Method Summary

#<(other) ⇒ Boolean

Returns true if hash is subset of other.
#<=(other) ⇒ Boolean

Returns true if hash is subset of other or equals to 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.
#>(other) ⇒ Boolean

Returns true if other is subset of hash.
#>=(other) ⇒ Boolean

Returns true if other is subset of hash or equals to hash.
#[](key) ⇒ value

Element Reference—Retrieves the value object corresponding to the key object.
#[]=(key, value) ⇒ value (also: #store)

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

See also Enumerable#any?
#assoc(obj) ⇒ Array^?

Searches through the hash comparing obj with the key using #==.
#clear ⇒ Hash

Removes all key-value pairs from hsh.
#compact ⇒ Hash

Returns a new hash with the nil values/key pairs removed.
#compact! ⇒ Hash^?

Removes all nil values from the 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.
#default=(obj) ⇒ Object

Sets the default value, the value returned for a key that does not exist in the hash.
#delete(key) ⇒ value

Deletes the key-value pair and returns the value from hsh whose key is equal to key.
#delete_if {|key, value| ... } ⇒ Hash

Deletes every key-value pair from hsh for which block evaluates to true.
#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.
#each {|key, value| ... } ⇒ Hash (also: #each_pair)

Calls block once for each key in hsh, passing the key-value pair as parameters.
#each_key {|key| ... } ⇒ Hash

Calls block once for each key in hsh, passing the key as a parameter.
#each_pair {|key, value| ... } ⇒ Hash

Alias for #each.
#each_value {|value| ... } ⇒ Hash

Calls block once for each key in hsh, passing the value as a parameter.
#eql?(other) ⇒ Boolean

Returns true if hash and other are both hashes with the same content.
#fetch(key [, default] ) ⇒ Object

Returns a value from the hash for the given key.
#fetch_values(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.
#flatten ⇒ Array

Returns a new array that is a one-dimensional flattening of this hash.
#has_key?(key) ⇒ Boolean

Alias for #key?.
#has_value?(value) ⇒ Boolean

Alias for #value?.
#hash ⇒ Integer

Compute a hash-code for this hash.
#include?(key) ⇒ Boolean

Alias for #key?.
#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.
#keep_if {|key, value| ... } ⇒ Hash

Deletes every key-value pair from hsh for which block evaluates to false.
#key(value) ⇒ key

Returns the key of an occurrence of a given value.
#key?(key) ⇒ Boolean (also: #include?, #member?, #has_key?)

Returns true if the given key is present in hsh.
#keys ⇒ Array

Returns a new array populated with the keys from this hash.
#length ⇒ Integer (also: #size)

Returns the number of key-value pairs in the hash.
#member?(key) ⇒ Boolean

Alias for #key?.
#merge(other_hash) ⇒ Hash

Returns a new hash containing the contents of other_hash and the contents of hsh.
#merge!(other_hash) ⇒ Hash (also: #update)

Adds the contents of other_hash to hsh.
#rassoc(obj) ⇒ Array^?

Searches through the hash comparing obj with the value using #==.
#rehash ⇒ Hash

Rebuilds the hash based on the current hash values for each key.
#reject {|key, value| ... } ⇒ Hash

Returns a new hash consisting of entries for which the block returns false.
#reject! {|key, value| ... } ⇒ Hash^?

Equivalent to #delete_if, but returns nil if no changes were made.
#replace(other_hash) ⇒ Hash

Replaces the contents of hsh with the contents of other_hash.
#select {|key, value| ... } ⇒ Hash

Returns a new hash consisting of entries for which the block returns true.
#select! {|key, value| ... } ⇒ Hash^?

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

Alias for #length.
#slice(*keys) ⇒ Hash

Returns a hash containing only the given keys and their values.
#store(key, value) ⇒ value

Alias for #[]=.
#to_a ⇒ Array

Converts hsh to a nested array of [ key, value ] arrays.
#to_h ⇒ Hash

Returns self.
#to_hash ⇒ Hash

Returns self.
#to_proc
#to_s ⇒ String (also: #inspect)

Return the contents of this hash as a string.
#transform_keys {|key| ... } ⇒ Hash

Returns a new hash with the results of running the block once for every key.
#transform_keys! {|key| ... } ⇒ Hash

Invokes the given block once for each key in hsh, replacing it with the new key returned by the block, and then returns hsh.
#transform_values {|value| ... } ⇒ Hash

Returns a new hash with the results of running the block once for every value.
#transform_values! {|value| ... } ⇒ Hash

Invokes the given block once for each value in hsh, replacing it with the new value returned by the block, and then returns hsh.
#update(other_hash) ⇒ Hash

Alias for #merge!.
#value?(value) ⇒ Boolean (also: #has_value?)

Returns true if the given value is present for some key in hsh.
#values ⇒ Array

Returns a new array populated with the values from hsh.
#values_at(key, ...) ⇒ Array

Return an array containing the values associated with the given keys.
#index(value) Internal use only
#initialize_copy(hash2) Internal use only

::Enumerable - Included

#all?	Passes each element of the collection to the given block.
#any?	Passes each element of the collection to the given block.
#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.
#find	Passes each entry in enum to block.
#find_all	Alias for Enumerable#select.
#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 a lazy enumerator, whose methods map/collect, flat_map/collect_concat, select/find_all, reject, grep, grep_v, zip, take, take_while, drop, and drop_while 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	Returns an array containing all elements of `enum` for which the given `block` returns a true value.
#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.
#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 629


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 669


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(tmp)->ntbl) {
		RHASH(hash)->ntbl = st_copy(RHASH(tmp)->ntbl);
	    }
	    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)) {
#if 0 /* refix in the next release */
		    rb_raise(rb_eArgError, "wrong element type %s at %ld (expected array)",
			     rb_builtin_class_name(e), i);

#else
		    rb_warn("wrong element type %s at %ld (expected array)",
			    rb_builtin_class_name(e), i);
		    rb_warn("ignoring wrong elements is deprecated, remove them explicitly");
		    rb_warn("this causes ArgumentError in the next release");
		    continue;
#endif
		}
		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);

    return hash;
}

.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 755


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 2920


static VALUE
rb_hash_compare_by_id(VALUE hash)
{
    st_table *identtable;
    if (rb_hash_compare_by_id_p(hash)) return hash;
    rb_hash_modify_check(hash);

    identtable = rb_init_identtable_with_size(RHASH_SIZE(hash));
    rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)identtable);
    if (RHASH(hash)->ntbl)
	st_free_table(RHASH(hash)->ntbl);
    RHASH(hash)->ntbl = identtable;

    return hash;
}

#compare_by_identity? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'hash.c', line 2945


VALUE
rb_hash_compare_by_id_p(VALUE hash)
{
    if (!RHASH(hash)->ntbl)
        return Qfalse;
    if (RHASH(hash)->ntbl->type == &identhash) {
	return Qtrue;
    }
    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 1019


static VALUE
rb_hash_default_proc(VALUE hash)
{
    if (FL_TEST(hash, HASH_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 1041


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 1751


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 3125


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 3104


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 2386


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 3167


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 3146


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 847


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

    if (!RHASH(hash)->ntbl || !st_lookup(RHASH(hash)->ntbl, key, &val)) {
	return rb_hash_default_value(hash, key);
    }
    return (VALUE)val;
}

#[]=(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 1632


VALUE
rb_hash_aset(VALUE hash, VALUE key, VALUE val)
{
    int iter_lev = RHASH_ITER_LEV(hash);
    st_table *tbl = RHASH(hash)->ntbl;

    rb_hash_modify(hash);
    if (!tbl) {
	if (iter_lev > 0) no_new_key();
	tbl = hash_tbl(hash);
    }
    if (tbl->type == &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`

#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 2709


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;
    table = RHASH(hash)->ntbl;
    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 1535


VALUE
rb_hash_clear(VALUE hash)
{
    rb_hash_modify_check(hash);
    if (!RHASH(hash)->ntbl)
        return hash;
    if (RHASH(hash)->ntbl->num_entries > 0) {
	if (RHASH_ITER_LEV(hash) > 0)
	    rb_hash_foreach(hash, clear_i, 0);
	else
	    st_clear(RHASH(hash)->ntbl);
    }

    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 2869


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 2891


static VALUE
rb_hash_compact_bang(VALUE hash)
{
    rb_hash_modify_check(hash);
    if (RHASH(hash)->ntbl) {
	st_index_t n = RHASH(hash)->ntbl->num_entries;
	rb_hash_foreach(hash, delete_if_nil, hash);
	if (n != RHASH(hash)->ntbl->num_entries)
	    return hash;
    }
    return Qnil;
}

#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 960


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, HASH_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 996


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 1166


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 1269


VALUE
rb_hash_delete_if(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    if (RHASH(hash)->ntbl)
	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 3061


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 1863


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 1816


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 1783


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 2401


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 904


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 (!RHASH(hash)->ntbl || !st_lookup(RHASH(hash)->ntbl, key, &val)) {
	if (block_given) return rb_yield(key);
	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);
	}
	return argv[1];
    }
    return (VALUE)val;
}

#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 1415


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;
}

#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 2806


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?).

#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 1102


static VALUE
rb_hash_index(VALUE hash, VALUE value)
{
    rb_warn("Hash#index is deprecated; use Hash#key");
    return rb_hash_key(hash, value);
}

#initialize_copy(hash2)

This method is for internal use only.

[ GitHub ]

# File 'hash.c', line 1661


static VALUE
rb_hash_initialize_copy(VALUE hash, VALUE hash2)
{
    st_table *ntbl;

    rb_hash_modify_check(hash);
    hash2 = to_hash(hash2);

    Check_Type(hash2, T_HASH);

    if (hash == hash2) return hash;

    ntbl = RHASH(hash)->ntbl;
    if (RHASH(hash2)->ntbl) {
	if (ntbl) st_free_table(ntbl);
        RHASH(hash)->ntbl = st_copy(RHASH(hash2)->ntbl);
	if (RHASH(hash)->ntbl->num_entries)
	    rb_hash_rehash(hash);
    }
    else if (ntbl) {
	st_clear(ntbl);
    }

    COPY_DEFAULT(hash, hash2);

    return hash;
}

#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 2479


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.

[ GitHub ]

# File 'hash.c', line 1508


VALUE
rb_hash_keep_if(VALUE hash)
{
    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    rb_hash_modify_check(hash);
    if (RHASH(hash)->ntbl)
	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 1088


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.

#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 2151


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

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

    if (ST_DATA_COMPATIBLE_P(VALUE)) {
	st_table *table = RHASH(hash)->ntbl;

	rb_gc_writebarrier_remember(keys);
	RARRAY_PTR_USE(keys, ptr, {
	    size = st_keys(table, ptr, size);
	});
	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.length        #=> 4
h.delete("a")   #=> 200
h.length        #=> 3

[ GitHub ]

# File 'hash.c', line 1734


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_hash) ⇒ `Hash` #merge(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`

Returns a new hash containing the contents of other_hash and the contents of hsh. If no block is specified, the value for entries with duplicate keys will be that of other_hash. Otherwise the value for each duplicate key is determined by calling the block with the key, its value in hsh and its value in other_hash.

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}
h1.merge(h2){|key, oldval, newval| newval - oldval}
               #=> {"a"=>100, "b"=>54,  "c"=>300}
h1             #=> {"a"=>100, "b"=>200}

[ GitHub ]

# File 'hash.c', line 2651


static VALUE
rb_hash_merge(VALUE hash1, VALUE hash2)
{
    return rb_hash_update(rb_hash_dup(hash1), hash2);
}

#merge!(other_hash) ⇒ `Hash` #update(other_hash) ⇒ `Hash` #merge!(other_hash) {|key, oldval, newval| ... } ⇒ `Hash` #update(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`
Also known as: #update

Adds the contents of other_hash to hsh. If no block is specified, entries with duplicate keys are overwritten with the values from other_hash, otherwise the value of each duplicate key is determined by calling the block with the key, its value in hsh and its value in other_hash.

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}
h1              #=> {"a"=>100, "b"=>254, "c"=>300}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2) { |key, v1, v2| v1 }
                #=> {"a"=>100, "b"=>200, "c"=>300}
h1              #=> {"a"=>100, "b"=>200, "c"=>300}

[ GitHub ]

# File 'hash.c', line 2563


static VALUE
rb_hash_update(VALUE hash1, VALUE hash2)
{
    rb_hash_modify(hash1);
    hash2 = to_hash(hash2);
    if (rb_block_given_p()) {
	rb_hash_foreach(hash2, rb_hash_update_block_i, hash1);
    }
    else {
	rb_hash_foreach(hash2, rb_hash_update_i, hash1);
    }
    return hash1;
}

#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 2767


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 795


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(hash)->ntbl)
        return hash;
    tmp = hash_alloc(0);
    tbl = st_init_table_with_size(RHASH(hash)->ntbl->type, RHASH(hash)->ntbl->num_entries);
    RHASH(tmp)->ntbl = tbl;

    rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tbl);
    st_free_table(RHASH(hash)->ntbl);
    RHASH(hash)->ntbl = tbl;
    RHASH(tmp)->ntbl = 0;

    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 1325


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 1288


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(hash)->ntbl->num_entries) return Qnil;
    return hash;
}

#replace(other_hash) ⇒ `Hash`

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 1701


static VALUE
rb_hash_replace(VALUE hash, VALUE hash2)
{
    st_table *table2;

    rb_hash_modify_check(hash);
    if (hash == hash2) return hash;
    hash2 = to_hash(hash2);

    COPY_DEFAULT(hash, hash2);

    table2 = RHASH(hash2)->ntbl;

    rb_hash_clear(hash);
    if (table2) hash_tbl(hash)->type = table2->type;
    rb_hash_foreach(hash2, replace_i, hash);

    return hash;
}

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

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}

[ GitHub ]

# File 'hash.c', line 1450


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

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

[ GitHub ]

# File 'hash.c', line 1481


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);
    if (!RHASH(hash)->ntbl)
        return Qnil;
    n = RHASH(hash)->ntbl->num_entries;
    rb_hash_foreach(hash, keep_if_i, hash);
    if (n == RHASH(hash)->ntbl->num_entries) return Qnil;
    return hash;
}

#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 1215


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

    rb_hash_modify_check(hash);
    if (RHASH(hash)->ntbl) {
	var.key = Qundef;
	if (RHASH_ITER_LEV(hash) == 0) {
	    if (st_shift(RHASH(hash)->ntbl, &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 1355


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 2034


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);
    OBJ_INFECT(ary, hash);

    return ary;
}

#to_h ⇒ `Hash`

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

[ GitHub ]

# File 'hash.c', line 2122


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

#to_hash ⇒ `Hash`

Returns self.

[ GitHub ]

# File 'hash.c', line 2108


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

#to_proc

[ GitHub ]

# File 'hash.c', line 3182


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 2093


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 1899


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 1932


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(hash)->ntbl) {
        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 1975


static VALUE
rb_hash_transform_values(VALUE hash)
{
    VALUE result;

    RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
    result = rb_hash_new_with_size(RHASH_SIZE(hash));
    if (!RHASH_EMPTY_P(hash)) {
        rb_hash_foreach(hash, transform_values_i, 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 2006


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(hash)->ntbl)
        rb_hash_foreach(hash, transform_values_i, hash);
    return hash;
}

#merge!(other_hash) ⇒ `Hash` #update(other_hash) ⇒ `Hash` #merge!(other_hash) {|key, oldval, newval| ... } ⇒ `Hash` #update(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`

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 2275


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 2195


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)) {
	st_table *table = RHASH(hash)->ntbl;

	rb_gc_writebarrier_remember(values);
	RARRAY_PTR_USE(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 1387


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;
}

Class: Hash

Overview

Common Uses

Hash Keys

Class Method Summary

Instance Attribute Summary

Instance Method Summary

::Enumerable - Included

Constructor Details

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

Class Method Details

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

.try_convert(obj) ⇒ Hash?

Instance Attribute Details

#compare_by_identity ⇒ Hash (readonly)

#compare_by_identity? ⇒ Boolean (readonly)

#default_proc ⇒ Object (rw)

#default_proc=(proc_obj or nil) (rw)

#empty? ⇒ Boolean (readonly)

Instance Method Details

#<(other) ⇒ Boolean

#<=(other) ⇒ Boolean

#==(other_hash) ⇒ Boolean

#>(other) ⇒ Boolean

#>=(other) ⇒ Boolean

#[](key) ⇒ value

#[]=(key, value) ⇒ value #store(key, value) ⇒ value Also known as: #store

Element Assignment

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

#assoc(obj) ⇒ Array?

#clear ⇒ Hash

#compact ⇒ Hash

#compact! ⇒ Hash?

#default(key = nil) ⇒ Object

#default=(obj) ⇒ Object

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

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

#dig(key, ...) ⇒ Object

#each {|key, value| ... } ⇒ Hash #each_pair {|key, value| ... } ⇒ Hash #each ⇒ Enumerator #each_pair ⇒ Enumerator Also known as: #each_pair

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

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

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

#eql?(other) ⇒ Boolean

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

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

#flatten ⇒ Array #flatten(level) ⇒ Array

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

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

#hash ⇒ Integer

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

#index(value)

#initialize_copy(hash2)

#to_s ⇒ String #inspect ⇒ String

#invert ⇒ Hash

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

#key(value) ⇒ key

#has_key?(key) ⇒ Boolean #include?(key) ⇒ Boolean #key?(key) ⇒ Boolean #member?(key) ⇒ Boolean Also known as: #include?, #member?, #has_key?

#keys ⇒ Array

#length ⇒ Integer #size ⇒ Integer Also known as: #size

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

#merge(other_hash) ⇒ Hash #merge(other_hash) {|key, oldval, newval| ... } ⇒ Hash

#merge!(other_hash) ⇒ Hash #update(other_hash) ⇒ Hash #merge!(other_hash) {|key, oldval, newval| ... } ⇒ Hash #update(other_hash) {|key, oldval, newval| ... } ⇒ Hash Also known as: #update

#rassoc(obj) ⇒ Array?

#rehash ⇒ Hash

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

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

#replace(other_hash) ⇒ Hash

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

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

#shift ⇒ Array, Object

#length ⇒ Integer #size ⇒ Integer

#slice(*keys) ⇒ Hash

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

#to_a ⇒ Array

#to_h ⇒ Hash

#to_hash ⇒ Hash

#to_proc

#to_s ⇒ String #inspect ⇒ String Also known as: #inspect

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

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

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

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

.try_convert(obj) ⇒ `Hash`^?

#compare_by_identity ⇒ `Hash` (readonly)

#compare_by_identity? ⇒ `Boolean` (readonly)

#empty? ⇒ `Boolean` (readonly)

#<(other) ⇒ `Boolean`

#<=(other) ⇒ `Boolean`

#==(other_hash) ⇒ `Boolean`

#>(other) ⇒ `Boolean`

#>=(other) ⇒ `Boolean`

#[](key) ⇒ `value`

#[]=(key, value) ⇒ `value` #store(key, value) ⇒ `value`
Also known as: #store

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

#assoc(obj) ⇒ Array^?

#clear ⇒ `Hash`

#compact ⇒ `Hash`

#compact! ⇒ `Hash`^?

#delete(key) ⇒ `value` #delete(key) {|key| ... } ⇒ `value`

#delete_if {|key, value| ... } ⇒ `Hash` #delete_if ⇒ Enumerator

#each {|key, value| ... } ⇒ `Hash` #each_pair {|key, value| ... } ⇒ `Hash` #each ⇒ Enumerator #each_pair ⇒ Enumerator
Also known as: #each_pair

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

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

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

#eql?(other) ⇒ `Boolean`

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

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

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

#invert ⇒ `Hash`

#keep_if {|key, value| ... } ⇒ `Hash` #keep_if ⇒ Enumerator

#has_key?(key) ⇒ `Boolean` #include?(key) ⇒ `Boolean` #key?(key) ⇒ `Boolean` #member?(key) ⇒ `Boolean`
Also known as: #include?, #member?, #has_key?

#length ⇒ Integer #size ⇒ Integer
Also known as: #size

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

#merge(other_hash) ⇒ `Hash` #merge(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`

#merge!(other_hash) ⇒ `Hash` #update(other_hash) ⇒ `Hash` #merge!(other_hash) {|key, oldval, newval| ... } ⇒ `Hash` #update(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`
Also known as: #update

#rassoc(obj) ⇒ Array^?

#rehash ⇒ `Hash`

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

#reject! {|key, value| ... } ⇒ `Hash`^? #reject! ⇒ Enumerator

#replace(other_hash) ⇒ `Hash`

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

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

#slice(*keys) ⇒ `Hash`

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

#to_h ⇒ `Hash`

#to_hash ⇒ `Hash`

#to_s ⇒ String #inspect ⇒ String
Also known as: #inspect

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

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

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

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

#merge!(other_hash) ⇒ `Hash` #update(other_hash) ⇒ `Hash` #merge!(other_hash) {|key, oldval, newval| ... } ⇒ `Hash` #update(other_hash) {|key, oldval, newval| ... } ⇒ `Hash`

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