Class: Hash

Inherits:
Object show all
Includes:
Enumerable
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 form when your keys are always 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 Hash.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 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 collapse

Instance Method Summary collapse

Methods included from Enumerable

#all?, #any?, #chunk, #collect, #collect_concat, #count, #cycle, #detect, #drop, #drop_while, #each_cons, #each_entry, #each_slice, #each_with_index, #each_with_object, #entries, #find, #find_all, #find_index, #first, #flat_map, #grep, #group_by, #inject, #lazy, #map, #max, #max_by, #min, #min_by, #minmax, #minmax_by, #none?, #one?, #partition, #reduce, #reverse_each, #slice_before, #sort, #sort_by, #take, #take_while, #zip

Constructor Details

#newObject #new(obj) ⇒ Object #new {|hash, key| ... } ⇒ Object

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"]

Overloads:


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# File 'hash.c', line 454

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();
	default_proc_arity_check(ifnone);
	RHASH_SET_IFNONE(hash, ifnone);
	FL_SET(hash, HASH_PROC_DEFAULT);
    }
    else {
	rb_scan_args(argc, argv, "01", &ifnone);
	RHASH_SET_IFNONE(hash, ifnone);
    }

    return hash;
}

Class Method Details

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

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}

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# File 'hash.c', line 495

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

    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);
    for (i=0; i<argc; i+=2) {
        rb_hash_aset(hash, argv[i], argv[i + 1]);
    }

    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

Returns:


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# File 'hash.c', line 583

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

Instance Method Details

#==(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

Returns:

  • (Boolean)

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# File 'hash.c', line 1978

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

#[](key) ⇒ Object

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

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

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# File 'hash.c', line 675

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

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

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

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) #=> {"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

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# File 'hash.c', line 1372

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;
}

#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

Returns:


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# File 'hash.c', line 2280

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];
}

#clearHash

Removes all key-value pairs from hsh.

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

Returns:


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# File 'hash.c', line 1303

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;
}

#compare_by_identityHash

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"]        #=> nil  # different objects.
h1[:c]         #=> "c"  # same symbols are all same.

Returns:


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# File 'hash.c', line 2412

static VALUE
rb_hash_compare_by_id(VALUE hash)
{
    if (rb_hash_compare_by_id_p(hash)) return hash;
    rb_hash_modify(hash);
    RHASH(hash)->ntbl->type = &identhash;
    rb_hash_rehash(hash);
    return hash;
}

#compare_by_identity?Boolean

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

Returns:

  • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 2431

static 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(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 Hash::new and Hash#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

Returns:


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# File 'hash.c', line 787

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

    rb_scan_args(argc, argv, "01", &key);
    ifnone = RHASH_IFNONE(hash);
    if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
	if (argc == 0) return Qnil;
	return rb_funcall(ifnone, id_yield, 2, hash, key);
    }
    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:[email protected]:6>
h["cat"]   #=> #<Proc:[email protected]:6>

Returns:


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# File 'hash.c', line 821

static VALUE
rb_hash_set_default(VALUE hash, VALUE ifnone)
{
    rb_hash_modify_check(hash);
    RHASH_SET_IFNONE(hash, ifnone);
    FL_UNSET(hash, HASH_PROC_DEFAULT);
    return ifnone;
}

#default_procObject

If Hash::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:[email protected]:1>
a = []                             #=> []
p.call(a, 2)
a                                  #=> [nil, nil, 4]

Returns:


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# File 'hash.c', line 845

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) ⇒ Object

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"

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# File 'hash.c', line 867

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

    rb_hash_modify_check(hash);
    if (NIL_P(proc)) {
	FL_UNSET(hash, HASH_PROC_DEFAULT);
	RHASH_SET_IFNONE(hash, proc);
	return proc;
    }
    b = rb_check_convert_type(proc, T_DATA, "Proc", "to_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;
    default_proc_arity_check(proc);
    RHASH_SET_IFNONE(hash, proc);
    FL_SET(hash, HASH_PROC_DEFAULT);
    return proc;
}

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

Deletes the key-value pair and returns the value from hsh whose key is equal to key. If the key is not found, returns the default value. 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"

Overloads:

  • #delete(key) {|key| ... } ⇒ Object

    Yields:


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# File 'hash.c', line 974

VALUE
rb_hash_delete(VALUE hash, VALUE key)
{
    VALUE val;

    rb_hash_modify_check(hash);
    val = rb_hash_delete_key(hash, key);
    if (val != Qundef) return val;
    if (rb_block_given_p()) {
	return rb_yield(key);
    }
    return Qnil;
}

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

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}

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1072

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;
}

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

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

Overloads:

  • #each {|key, value| ... } ⇒ Hash

    Yields:

    Returns:

  • #each_pair {|key, value| ... } ⇒ Hash

    Yields:

    Returns:


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# File 'hash.c', line 1608

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_keyObject

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

Overloads:

  • #each_key {|key| ... } ⇒ Hash

    Yields:

    Returns:


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# File 'hash.c', line 1564

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 #eachObject #each_pairObject

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

Overloads:

  • #each {|key, value| ... } ⇒ Hash

    Yields:

    Returns:

  • #each_pair {|key, value| ... } ⇒ Hash

    Yields:

    Returns:


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# File 'hash.c', line 1608

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_value {|value| ... } ⇒ Hash #each_valueObject

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

Overloads:

  • #each_value {|value| ... } ⇒ Hash

    Yields:

    • (value)

    Returns:


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# File 'hash.c', line 1531

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;
}

#empty?Boolean

Returns true if hsh contains no key-value pairs.

{}.empty?   #=> true

Returns:

  • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1499

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

#eql?(other) ⇒ Boolean

Returns true if hash and other are both hashes with the same content.

Returns:

  • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1992

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 an 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

Overloads:


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# File 'hash.c', line 732

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

    rb_scan_args(argc, argv, "11", &key, &if_none);

    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) {
	    volatile 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_raise(rb_eKeyError, "key not found: %"PRIsVALUE, desc);
	}
	return if_none;
    }
    return (VALUE)val;
}

#flattenArray #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"]

Overloads:


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# File 'hash.c', line 2377

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

    ary = rb_ary_new_capa(RHASH_SIZE(hash) * 2);
    rb_hash_foreach(hash, flatten_i, ary);
    if (argc) {
	int level = NUM2INT(*argv) - 1;
	if (level > 0) {
	    *argv = INT2FIX(level);
	    rb_funcall2(ary, rb_intern("flatten!"), argc, argv);
	}
    }
    return ary;
}

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

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

Overloads:

  • #has_key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #include?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #member?(key) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1844

static VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
    if (!RHASH(hash)->ntbl)
        return Qfalse;
    if (st_lookup(RHASH(hash)->ntbl, key, 0)) {
	return Qtrue;
    }
    return Qfalse;
}

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

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

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

Overloads:

  • #has_value?(value) ⇒ Boolean

    Returns:

    • (Boolean)
  • #value?(value) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1880

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];
}

#hashFixnum

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

Returns:


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# File 'hash.c', line 2018

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 INT2FIX(hval);
}

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

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

Overloads:

  • #has_key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #include?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #member?(key) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1844

static VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
    if (!RHASH(hash)->ntbl)
        return Qfalse;
    if (st_lookup(RHASH(hash)->ntbl, key, 0)) {
	return Qtrue;
    }
    return Qfalse;
}

#indexObject

:nodoc:


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# File 'hash.c', line 931

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_copyObject

:nodoc:


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# File 'hash.c', line 1401

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);

    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);
    }

    if (FL_TEST(hash2, HASH_PROC_DEFAULT)) {
        FL_SET(hash, HASH_PROC_DEFAULT);
    }
    else {
	FL_UNSET(hash, HASH_PROC_DEFAULT);
    }
    RHASH_SET_IFNONE(hash, RHASH_IFNONE(hash2));

    return hash;
}

#to_sString #inspectString Also known as: to_s

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}"

Overloads:


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# File 'hash.c', line 1696

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);
}

#invertObject

Returns a new hash created by using hsh's values as keys, and the keys as values.

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

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# File 'hash.c', line 2050

static VALUE
rb_hash_invert(VALUE hash)
{
    VALUE h = rb_hash_new();

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

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

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

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

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1276

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) ⇒ Object

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

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# File 'hash.c', line 917

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

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

Overloads:

  • #has_key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #include?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #member?(key) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1844

static VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
    if (!RHASH(hash)->ntbl)
        return Qfalse;
    if (st_lookup(RHASH(hash)->ntbl, key, 0)) {
	return Qtrue;
    }
    return Qfalse;
}

#keysArray

Returns a new array populated with the keys from this hash. See also Hash#values.

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

Returns:


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# File 'hash.c', line 1760

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;

	if (OBJ_PROMOTED(keys)) rb_gc_writebarrier_remember_promoted(keys);
	RARRAY_PTR_USE(keys, ptr, {
	    size = st_keys_check(table, ptr, size, Qundef);
	});
	rb_ary_set_len(keys, size);
    }
    else {
	rb_hash_foreach(hash, keys_i, keys);
    }

    return keys;
}

#lengthFixnum #sizeFixnum

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

Overloads:


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# File 'hash.c', line 1482

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

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

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

Overloads:

  • #has_key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #include?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #key?(key) ⇒ Boolean

    Returns:

    • (Boolean)
  • #member?(key) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1844

static VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
    if (!RHASH(hash)->ntbl)
        return Qfalse;
    if (st_lookup(RHASH(hash)->ntbl, key, 0)) {
	return Qtrue;
    }
    return Qfalse;
}

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

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}

Overloads:

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

    Yields:

    • (key, oldval, newval)

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# File 'hash.c', line 2222

static VALUE
rb_hash_merge(VALUE hash1, VALUE hash2)
{
    return rb_hash_update(rb_obj_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

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

Overloads:

  • #merge!(other_hash) ⇒ Hash

    Returns:

  • #update(other_hash) ⇒ Hash

    Returns:

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

    Yields:

    • (key, oldval, newval)

    Returns:

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

    Yields:

    • (key, oldval, newval)

    Returns:


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# File 'hash.c', line 2133

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

Returns:


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# File 'hash.c', line 2338

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];
}

#rehashHash

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 Hash#rehash is called while an iterator is traversing the hash, an 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

Returns:


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# File 'hash.c', line 623

static 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 #rejectObject

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}

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1128

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_MISC_ATTRIBUTES(hash, klass)) {
#if HASH_REJECT_COPY_MISC_ATTRIBUTES
	    rb_warn("copying unguaranteed attributes: %+"PRIsVALUE, hash);
	    rb_warn("following atributes will not be copied in the future version:");
	    if (klass != rb_cHash) {
		rb_warn("  subclass: %+"PRIsVALUE, klass);
	    }
	    if (FL_TEST(hash, FL_EXIVAR)) {
		rb_warn("  instance variables: %+"PRIsVALUE,
			rb_obj_instance_variables(hash));
	    }
	    if (FL_TEST(hash, FL_TAINT)) {
		rb_warn("  taintedness");
	    }
	    if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
		rb_warn("  default proc: %+"PRIsVALUE, RHASH_IFNONE(hash));
	    }
	    else if (!NIL_P(RHASH_IFNONE(hash)))
		rb_warn("  default value: %+"PRIsVALUE, RHASH_IFNONE(hash));
#else
	    rb_warn("unguaranteed attributes are not copied: %+"PRIsVALUE, hash);
	    rb_warn("following atributes are ignored now:");
#endif
	}
    }
#if HASH_REJECT_COPY_MISC_ATTRIBUTES
    result = rb_hash_dup_empty(hash);
#else
    result = rb_hash_new();
#endif
    if (!RHASH_EMPTY_P(hash)) {
	rb_hash_foreach(hash, reject_i, result);
    }
    return result;
}

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

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

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1091

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}

Returns:


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# File 'hash.c', line 1445

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);

    RHASH_SET_IFNONE(hash, RHASH_IFNONE(hash2));
    if (FL_TEST(hash2, HASH_PROC_DEFAULT))
	FL_SET(hash, HASH_PROC_DEFAULT);
    else
	FL_UNSET(hash, HASH_PROC_DEFAULT);

    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 #selectObject

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}

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1218

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!Object

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

Overloads:

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

    Yields:

    Returns:


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# File 'hash.c', line 1249

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;
}

#shiftArray, 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"}

Returns:


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# File 'hash.c', line 1016

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_key(hash, var.key);
		return rb_assoc_new(var.key, var.val);
	    }
	}
    }
    return hash_default_value(hash, Qnil);
}

#lengthFixnum #sizeFixnum

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

Overloads:


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# File 'hash.c', line 1482

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

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

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) #=> {"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

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# File 'hash.c', line 1372

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;
}

#to_aArray

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]]

Returns:


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# File 'hash.c', line 1637

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_hHash

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

Returns:


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# File 'hash.c', line 1725

static VALUE
rb_hash_to_h(VALUE hash)
{
    if (rb_obj_class(hash) != rb_cHash) {
	VALUE ret = rb_hash_new();
	if (!RHASH_EMPTY_P(hash))
	    RHASH(ret)->ntbl = st_copy(RHASH(hash)->ntbl);
	if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
	    FL_SET(ret, HASH_PROC_DEFAULT);
	}
	RHASH_SET_IFNONE(ret, RHASH_IFNONE(hash));
	return ret;
    }
    return hash;
}

#to_hashHash

Returns self.

Returns:


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# File 'hash.c', line 1711

static VALUE
rb_hash_to_hash(VALUE 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

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

Overloads:

  • #merge!(other_hash) ⇒ Hash

    Returns:

  • #update(other_hash) ⇒ Hash

    Returns:

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

    Yields:

    • (key, oldval, newval)

    Returns:

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

    Yields:

    • (key, oldval, newval)

    Returns:


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# File 'hash.c', line 2133

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;
}

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

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

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

Overloads:

  • #has_value?(value) ⇒ Boolean

    Returns:

    • (Boolean)
  • #value?(value) ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean)

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# File 'hash.c', line 1880

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];
}

#valuesArray

Returns a new array populated with the values from hsh. See also Hash#keys.

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

Returns:


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# File 'hash.c', line 1804

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;

	if (OBJ_PROMOTED(values)) rb_gc_writebarrier_remember_promoted(values);
	RARRAY_PTR_USE(values, ptr, {
	    size = st_values_check(table, ptr, size, Qundef);
	});
	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 Hash.select.

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

Returns:


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# File 'hash.c', line 1183

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;
}