class Hash - Documentation for Ruby 2.3.0 (original) (raw)

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]

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"]

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 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

Public Class Methods

Hash[ key, value, ... ] → new_hash click to toggle source

Hash[ [ [key, value], ... ] ] → new_hash

Hash[ object ] → new_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]
Hash[ [ ["a", 100], ["b", 200] ] ]
Hash["a" => 100, "b" => 200]

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;

}

new → new_hash click to toggle source

new(obj) → new_hash

new {|hash, key| block } → new_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"]
h["c"]

h["c"].upcase!
h["d"]
h.keys

h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" } h["c"]
h["c"].upcase!
h["d"]
h.keys

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_check_arity(argc, 0, 1);
    ifnone = argc == 0 ? Qnil : argv[0];
    RHASH_SET_IFNONE(hash, ifnone);
}

return hash;

}

try_convert(obj) → hash or nil click to toggle source

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})
Hash.try_convert("1=>2")

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

Public Instance Methods

hash < other → true or false click to toggle source

Returns true if hash is subset of other.

h1 = {a:1, b:2} h2 = {a:1, b:2, c:3} h1 < h2
h2 < h1
h1 < h1

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); }

hash <= other → true or false click to toggle source

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
h2 <= h1
h1 <= h1

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); }

hsh == other_hash → true or false click to toggle source

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
h2 == h3
h3 == h4

The orders of each hashes are not compared.

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

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

hash > other → true or false click to toggle source

Returns true if other is subset of hash.

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

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); }

hash >= other → true or false click to toggle source

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
h2 >= h1
h1 >= h1

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); }

hsh[key] → value click to toggle source

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"]
h["c"]

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;

}

hsh[key] = value → value click to toggle source

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
h.store("d", 42) h

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 h.key(200).equal? b

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)| block }] → true or false click to toggle source

See also Enumerable#any?

static VALUE rb_hash_any_p(VALUE hash) { VALUE ret = Qfalse;

if (RHASH_EMPTY_P(hash)) return Qfalse;
if (!rb_block_given_p()) {
    /* yields pairs, never false */
    return Qtrue;
}
if (rb_block_arity() > 1)
    rb_hash_foreach(hash, any_p_i_fast, (VALUE)&ret);
else
    rb_hash_foreach(hash, any_p_i, (VALUE)&ret);
return ret;

}

assoc(obj) → an_array or nil click to toggle source

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")
h.assoc("foo")

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 → hsh click to toggle source

Removes all key-value pairs from hsh.

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

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_identity → hsh click to toggle source

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"]
h1.compare_by_identity h1.compare_by_identity? h1["a".dup]
h1[:c]

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? → true or false click to toggle source

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

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) → obj click to toggle source

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

h = Hash.new
h.default
h.default(2)

h = Hash.new("cat")
h.default
h.default(2)

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

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 → obj click to toggle source

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"]
h["z"]

h.default = proc do |hash, key| hash[key] = key + key end h[2]
h["cat"]

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_proc → anObject click to toggle source

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
a = []
p.call(a, 2) a

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 click to toggle source

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]
h["cat"]

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) → value click to toggle source

delete(key) {| key | block } → 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")
h.delete("z")
h.delete("z") { |el| "#{el} not found" }

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 | block } → hsh click to toggle source

delete_if → an_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" }

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 click to toggle source

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)
h.dig(:foo, :zot, :xyz)

g = { foo: [10, 11, 12] } g.dig(:foo, 1)
g.dig(:foo, 1, 0)
g.dig(:foo, :bar)

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 | block } → hsh click to toggle source

each_pair {| key, value | block } → hsh

each → an_enumerator

each_pair → an_enumerator

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

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 | block } → hsh click to toggle source

each_key → an_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

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_pair {| key, value | block } → hsh click to toggle source

each_pair → an_enumerator

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

each_value {| value | block } → hsh click to toggle source

each_value → an_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

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? → true or false click to toggle source

Returns true if hsh contains no key-value pairs.

{}.empty?

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

eql?(other) → true or false click to toggle source

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

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

fetch(key [, default] ) → obj click to toggle source

fetch(key) {| key | block } → obj

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")
h.fetch("z", "go fish")
h.fetch("z") { |el| "go fish, #{el}"}

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

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_raise(rb_eKeyError, "key not found: %"PRIsVALUE, desc);
    }
    return argv[1];
}
return (VALUE)val;

}

fetch_values(key, ...) → array click to toggle source

fetch_values(key, ...) { |key| block } → 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 Hash#values_at and Hash#fetch.

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

h.fetch_values("cow", "cat")
h.fetch_values("cow", "bird")
h.fetch_values("cow", "bird") { |k| k.upcase }

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 → an_array click to toggle source

flatten(level) → an_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
a.flatten(2)

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

if (argc) {
    int level = NUM2INT(*argv);
    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);
    if (level - 1 > 0) {
        *argv = INT2FIX(level - 1);
        rb_funcall2(ary, id_flatten_bang, argc, argv);
    }
    else if (level < 0) {
        rb_funcall2(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) → true or false click to toggle source

Returns true if the given key is present in hsh.

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

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

See also Enumerable#include?

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) → true or false click to toggle source

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

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

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];

}

hash → fixnum click to toggle source

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

See also Enumerable#include?

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; }

to_s → string click to toggle source

inspect → string

Return the contents of this hash as a string.

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

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); }

Also aliased as: to_s

invert → new_hash click to toggle source

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

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 | block } → hsh click to toggle source

keep_if → an_enumerator

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

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

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 click to toggle source

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)
h.key(300)
h.key(999)

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];

}

key?(key) → true or false click to toggle source

Returns true if the given key is present in hsh.

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

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

See also Enumerable#include?

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; }

keys → array click to toggle source

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

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_check(table, ptr, size, Qundef);
    });
    rb_ary_set_len(keys, size);
}
else {
    rb_hash_foreach(hash, keys_i, keys);
}

return keys;

}

length → fixnum click to toggle source

Returns the number of key-value pairs in the hash.

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

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

member?(key) → true or false click to toggle source

Returns true if the given key is present in hsh.

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

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

See also Enumerable#include?

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) → new_hash click to toggle source

merge(other_hash){|key, oldval, newval| block} → new_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)
h1.merge(h2){|key, oldval, newval| newval - oldval}

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

merge!(other_hash) → hsh click to toggle source

merge!(other_hash){|key, oldval, newval| block} → hsh

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)

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

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) → an_array or nil click to toggle source

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")
a.rassoc("four")

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 → hsh click to toggle source

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, a RuntimeError will be raised in the iterator.

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

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| block} → a_hash click to toggle source

reject → an_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"}
h.reject {|k,v| v > 100}

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 | block } → hsh or nil click to toggle source

reject! → an_enumerator

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

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) → hsh click to toggle source

Replaces the contents of hsh with the contents of other_hash.

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

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| block} → a_hash click to toggle source

select → an_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"}
h.select {|k,v| v < 200}

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 | block } → hsh or nil click to toggle source

select! → an_enumerator

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

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 → anArray or obj click to toggle source

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
h

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);

}

size → fixnum click to toggle source

Returns the number of key-value pairs in the hash.

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

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

store(key, value) → value click to toggle source

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
h.store("d", 42) h

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 h.key(200).equal? b

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_a → array click to toggle source

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

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

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 → hsh or new_hash click to toggle source

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

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_hash → hsh click to toggle source

Returns self.

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

to_proc() click to toggle source

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

update(other_hash) → hsh click to toggle source

update(other_hash){|key, oldval, newval| block} → hsh

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

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

value?(value) → true or false click to toggle source

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

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

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 click to toggle source

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

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

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_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 click to toggle source

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")

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;

}