A Hash maps each of its unique keys to a specific value.
A Hash has certain similarities to an Array, but:
Hash Data Syntax¶ ↑
The older syntax for Hash data uses the âhash rocket,â =>:
h = {:foo => 0, :bar => 1, :baz => 2}
h
Alternatively, but only for a Hash key thatâs a Symbol, you can use a newer JSON-style syntax, where each bareword becomes a Symbol:
h = {foo: 0, bar: 1, baz: 2}
h
You can also use a String in place of a bareword:
h = {'foo': 0, 'bar': 1, 'baz': 2}
h
And you can mix the styles:
h = {foo: 0, :bar => 1, 'baz': 2}
h
But itâs an error to try the JSON-style syntax for a key thatâs not a bareword or a String:
# Raises SyntaxError (syntax error, unexpected ':', expecting =>):
h = {0: 'zero'}
Hash value can be omitted, meaning that value will be fetched from the context by the name of the key:
x = 0
y = 100
h = {x:, y:}
h
Common Uses¶ ↑
You can use a Hash to give names to objects:
person = {name: 'Matz', language: 'Ruby'}
person
You can use a Hash to give names to method arguments:
def some_method(hash)
p hash
end
some_method({foo: 0, bar: 1, baz: 2})
Note: when the last argument in a method call is a Hash, the curly braces may be omitted:
some_method(foo: 0, bar: 1, baz: 2)
You can use a Hash to initialize an object:
class Dev
attr_accessor :name, :language
def initialize(hash)
self.name = hash[:name]
self.language = hash[:language]
end
end
matz = Dev.new(name: 'Matz', language: 'Ruby')
matz
Creating a Hash¶ ↑
You can create a Hash object explicitly with:
A hash literal.
You can convert certain objects to Hashes with:
Method Hash.
You can create a Hash by calling method Hash.new.
Create an empty Hash:
h = Hash.new h h.class
You can create a Hash by calling method Hash.[].
Create an empty Hash:
h = Hash[] h
Create a Hash with initial entries:
h = Hash[foo: 0, bar: 1, baz: 2] h
You can create a Hash by using its literal form (curly braces).
Create an empty Hash:
h = {}
h
Create a Hash with initial entries:
h = {foo: 0, bar: 1, baz: 2}
h
Hash Value Basics¶ ↑
The simplest way to retrieve a Hash value (instance method []):
h = {foo: 0, bar: 1, baz: 2}
h[:foo]
The simplest way to create or update a Hash value (instance method []=):
h = {foo: 0, bar: 1, baz: 2}
h[:bat] = 3
h
h[:foo] = 4
h
The simplest way to delete a Hash entry (instance method delete):
h = {foo: 0, bar: 1, baz: 2}
h.delete(:bar)
h
Entry Order¶ ↑
A Hash object presents its entries in the order of their creation. This is seen in:
Iterative methods such as each, each_key, each_pair, each_value.
Other order-sensitive methods such as shift, keys, values.
The String returned by method inspect.
A new Hash has its initial ordering per the given entries:
h = Hash[foo: 0, bar: 1] h
New entries are added at the end:
h[:baz] = 2 h
Updating a value does not affect the order:
h[:baz] = 3 h
But re-creating a deleted entry can affect the order:
h.delete(:foo) h[:foo] = 5 h
Hash Keys¶ ↑ Hash Key Equivalence¶ ↑
Two objects are treated as the same hash key when their hash value is identical and the two objects are eql? to each other.
Hash Key¶ ↑
Modifying a Hash key while it is in use damages the hashâs index.
This Hash has keys that are Arrays:
a0 = [ :foo, :bar ]
a1 = [ :baz, :bat ]
h = {a0 => 0, a1 => 1}
h.include?(a0)
h[a0]
a0.hash
Modifying array element a0[0] changes its hash value:
a0[0] = :bam a0.hash
And damages the Hash index:
h.include?(a0) h[a0]
You can repair the hash index using method rehash:
h.rehash h.include?(a0) h[a0]
A String key is always safe. Thatâs because an unfrozen String passed as a key will be replaced by a duplicated and frozen String:
s = 'foo'
s.frozen?
h = {s => 0}
first_key = h.keys.first
first_key.frozen?
User-Defined Hash Keys¶ ↑
To be usable as a Hash key, objects must implement the methods hash and eql?. Note: this requirement does not apply if the Hash uses compare_by_identity since comparison will then rely on the keysâ object id instead of hash and eql?.
Object defines basic implementation for hash and eq? that makes each object a distinct key. Typically, user-defined classes will want to override these methods to provide meaningful behavior, or for example inherit Struct that has useful definitions for these.
A typical implementation of hash is based on the objectâs data while eql? is usually aliased to the overridden == method:
class Book
attr_reader :author, :title
def initialize(author, title)
@author = author
@title = title
end
def ==(other)
self.class === other &&
other.author == @author &&
other.title == @title
end
alias eql? ==
def hash
[self.class, @author, @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
Default Values¶ ↑
The methods [], values_at and dig need to return the value associated to a certain key. When that key is not found, that value will be determined by its default proc (if any) or else its default (initially ânil`).
You can retrieve the default value with method default:
h = Hash.new h.default
You can set the default value by passing an argument to method Hash.new or with method default=
h = Hash.new(-1) h.default h.default = 0 h.default
This default value is returned for [], values_at and dig when a key is not found:
counts = {foo: 42}
counts.default
counts[:foo] = 42
counts[:bar]
counts.default = 0
counts[:bar]
counts.values_at(:foo, :bar, :baz)
counts.dig(:bar)
Note that the default value is used without being duplicated. It is not advised to set the default value to a mutable object:
synonyms = Hash.new([]) synonyms[:hello] synonyms[:hello] << :hi synonyms.default synonyms[:world] << :universe synonyms[:world] synonyms.keys
To use a mutable object as default, it is recommended to use a default proc
DefaultProc¶ ↑
When the default proc for a Hash is set (i.e., not nil), the default value returned by method [] is determined by the default proc alone.
You can retrieve the default proc with method default_proc:
h = Hash.new h.default_proc
You can set the default proc by calling Hash.new with a block or calling the method default_proc=
h = Hash.new { |hash, key| "Default value for #{key}" }
h.default_proc.class
h.default_proc = proc { |hash, key| "Default value for #{key.inspect}" }
h.default_proc.class
When the default proc is set (i.e., not nil) and method [] is called with with a non-existent key, [] calls the default proc with both the Hash object itself and the missing key, then returns the procâs return value:
h = Hash.new { |hash, key| "Default value for #{key}" }
h[:nosuch]
Note that in the example above no entry for key :nosuch is created:
h.include?(:nosuch)
However, the proc itself can add a new entry:
synonyms = Hash.new { |hash, key| hash[key] = [] }
synonyms.include?(:hello)
synonyms[:hello] << :hi
synonyms[:world] << :universe
synonyms.keys
Note that setting the default proc will clear the default value and vice versa.
Be aware that a default proc that modifies the hash is not thread-safe in the sense that multiple threads can call into the default proc concurrently for the same key.
Whatâs Here¶ ↑First, whatâs elsewhere. Class Hash:
Inherits from class Object.
Includes module Enumerable, which provides dozens of additional methods.
Here, class Hash provides methods that are useful for:
Class Hash also includes methods from module Enumerable.
Hash¶ ↑
::[]: Returns a new hash populated with given objects.
::new: Returns a new empty hash.
::try_convert: Returns a new hash created from a given object.
Hash State¶ ↑
compare_by_identity: Sets self to consider only identity in comparing keys.
default=: Sets the default to a given value.
default_proc=: Sets the default proc to a given proc.
rehash: Rebuilds the hash table by recomputing the hash index for each key.
any?: Returns whether any element satisfies a given criterion.
compare_by_identity?: Returns whether the hash considers only identity when comparing keys.
default: Returns the default value, or the default value for a given key.
default_proc: Returns the default proc.
empty?: Returns whether there are no entries.
eql?: Returns whether a given object is equal to self.
hash: Returns the integer hash code.
has_value? (aliased as value?): Returns whether a given object is a value in self.
include? (aliased as has_key?, member?, key?): Returns whether a given object is a key in self.
<: Returns whether self is a proper subset of a given object.
<=: Returns whether self is a subset of a given object.
==: Returns whether a given object is equal to self.
>: Returns whether self is a proper superset of a given object
>=: Returns whether self is a superset of a given object.
[]: Returns the value associated with a given key.
assoc: Returns a 2-element array containing a given key and its value.
dig: Returns the object in nested objects that is specified by a given key and additional arguments.
fetch: Returns the value for a given key.
fetch_values: Returns array containing the values associated with given keys.
key: Returns the key for the first-found entry with a given value.
keys: Returns an array containing all keys in self.
rassoc: Returns a 2-element array consisting of the key and value of the first-found entry having a given value.
values: Returns an array containing all values in self/
values_at: Returns an array containing values for given keys.
[]= (aliased as store): Associates a given key with a given value.
merge: Returns the hash formed by merging each given hash into a copy of self.
update (aliased as merge!): Merges each given hash into self.
replace (aliased as initialize_copy): Replaces the entire contents of self with the contents of a given hash.
These methods remove entries from self:
clear: Removes all entries from self.
compact!: Removes all nil-valued entries from self.
delete: Removes the entry for a given key.
delete_if: Removes entries selected by a given block.
select! (aliased as filter!): Keep only those entries selected by a given block.
keep_if: Keep only those entries selected by a given block.
reject!: Removes entries selected by a given block.
shift: Removes and returns the first entry.
These methods return a copy of self with some entries removed:
compact: Returns a copy of self with all nil-valued entries removed.
except: Returns a copy of self with entries removed for specified keys.
select (aliased as filter): Returns a copy of self with only those entries selected by a given block.
reject: Returns a copy of self with entries removed as specified by a given block.
slice: Returns a hash containing the entries for given keys.
each_pair (aliased as each): Calls a given block with each key-value pair.
each_key: Calls a given block with each key.
each_value: Calls a given block with each value.
inspect (aliased as to_s): Returns a new String containing the hash entries.
to_a: Returns a new array of 2-element arrays; each nested array contains a key-value pair from self.
to_h: Returns self if a Hash; if a subclass of Hash, returns a Hash containing the entries from self.
to_hash: Returns self.
to_proc: Returns a proc that maps a given key to its value.
transform_keys: Returns a copy of self with modified keys.
transform_keys!: Modifies keys in self
transform_values: Returns a copy of self with modified values.
transform_values!: Modifies values in self.
flatten: Returns an array that is a 1-dimensional flattening of self.
invert: Returns a hash with the each key-value pair inverted.
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)) {
if (!RHASH_EMPTY_P(tmp) && rb_hash_compare_by_id_p(tmp)) {
/* hash_copy for non-empty hash will copy compare_by_identity
flag, but we don't want it copied. Work around by
converting hash to flattened array and using that. */
tmp = rb_hash_to_a(tmp);
}
else {
hash = hash_alloc(klass);
if (!RHASH_EMPTY_P(tmp))
hash_copy(hash, tmp);
return hash;
}
}
else {
tmp = rb_check_array_type(argv[0]);
}
if (!NIL_P(tmp)) {
long i;
hash = hash_alloc(klass);
for (i = 0; i < RARRAY_LEN(tmp); ++i) {
VALUE e = RARRAY_AREF(tmp, i);
VALUE v = rb_check_array_type(e);
VALUE key, val = Qnil;
if (NIL_P(v)) {
rb_raise(rb_eArgError, "wrong element type %s at %ld (expected array)",
rb_builtin_class_name(e), i);
}
switch (RARRAY_LEN(v)) {
default:
rb_raise(rb_eArgError, "invalid number of elements (%ld for 1..2)",
RARRAY_LEN(v));
case 2:
val = RARRAY_AREF(v, 1);
case 1:
key = RARRAY_AREF(v, 0);
rb_hash_aset(hash, key, val);
}
}
return hash;
}
}
if (argc % 2 != 0) {
rb_raise(rb_eArgError, "odd number of arguments for Hash");
}
hash = hash_alloc(klass);
rb_hash_bulk_insert(argc, argv, hash);
hash_verify(hash);
return hash;
}
Returns a new Hash object populated with the given objects, if any. See Hash::new.
With no argument, returns a new empty Hash.
When the single given argument is a Hash, returns a new Hash populated with the entries from the given Hash, excluding the default value or proc.
h = {foo: 0, bar: 1, baz: 2}
Hash[h]
When the single given argument is an Array of 2-element Arrays, returns a new Hash object wherein each 2-element array forms a key-value entry:
Hash[ [ [:foo, 0], [:bar, 1] ] ]
When the argument count is an even number; returns a new Hash object wherein each successive pair of arguments has become a key-value entry:
Hash[:foo, 0, :bar, 1]
Raises an exception if the argument list does not conform to any of the above.
Sourcedef initialize(ifnone = (ifnone_unset = true), capacity: 0, &block) Primitive.rb_hash_init(capacity, ifnone_unset, ifnone, block) end
Returns a new empty Hash object.
The initial default value and initial default proc for the new hash depend on which form above was used. See Default Values.
If neither an argument nor a block is given, initializes both the default value and the default proc to nil:
h = Hash.new h.default h.default_proc
If argument default_value is given but no block is given, initializes the default value to the given default_value and the default proc to nil:
h = Hash.new(false) h.default h.default_proc
If a block is given but no default_value, stores the block as the default proc and sets the default value to nil:
h = Hash.new {|hash, key| "Default value for #{key}" }
h.default
h.default_proc.class
h[:nosuch]
If both a block and a default_value are given, raises an ArgumentError
If the optional keyword argument capacity is given, the hash will be allocated with enough capacity to accommodate this many keys without having to be resized.
static VALUE
rb_hash_s_ruby2_keywords_hash(VALUE dummy, VALUE hash)
{
Check_Type(hash, T_HASH);
VALUE tmp = rb_hash_dup(hash);
if (RHASH_EMPTY_P(hash) && rb_hash_compare_by_id_p(hash)) {
rb_hash_compare_by_id(tmp);
}
RHASH(tmp)->basic.flags |= RHASH_PASS_AS_KEYWORDS;
return tmp;
}
Duplicates a given hash and adds a ruby2_keywords flag. This method is not for casual use; debugging, researching, and some truly necessary cases like deserialization of arguments.
h = {k: 1}
h = Hash.ruby2_keywords_hash(h)
def foo(k: 42)
k
end
foo(*[h])
Source
static VALUE
rb_hash_s_ruby2_keywords_hash_p(VALUE dummy, VALUE hash)
{
Check_Type(hash, T_HASH);
return RBOOL(RHASH(hash)->basic.flags & RHASH_PASS_AS_KEYWORDS);
}
Checks if a given hash is flagged by Module#ruby2_keywords (or Proc#ruby2_keywords). This method is not for casual use; debugging, researching, and some truly necessary cases like serialization of arguments.
ruby2_keywords def foo(*args)
Hash.ruby2_keywords_hash?(args.last)
end
foo(k: 1)
foo({k: 1})
Source
static VALUE
rb_hash_s_try_convert(VALUE dummy, VALUE hash)
{
return rb_check_hash_type(hash);
}
If obj is a Hash object, returns obj.
Otherwise if obj responds to :to_hash, calls obj.to_hash and returns the result.
Returns nil if obj does not respond to :to_hash
Raises an exception unless obj.to_hash returns a Hash object.
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);
}
Returns true if hash is a proper subset of other_hash, false otherwise:
h1 = {foo: 0, bar: 1}
h2 = {foo: 0, bar: 1, baz: 2}
h1 < h2
h2 < h1
h1 < h1
Source
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);
}
Returns true if hash is a subset of other_hash, false otherwise:
h1 = {foo: 0, bar: 1}
h2 = {foo: 0, bar: 1, baz: 2}
h1 <= h2
h2 <= h1
h1 <= h1
Source
static VALUE
rb_hash_equal(VALUE hash1, VALUE hash2)
{
return hash_equal(hash1, hash2, FALSE);
}
Returns true if all of the following are true:
object is a Hash object.
hash and object have the same keys (regardless of order).
For each key key, hash[key] == object[key].
Otherwise, returns false.
Equal:
h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1, baz: 2}
h1 == h2
h3 = {baz: 2, bar: 1, foo: 0}
h1 == h3
Source
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);
}
Returns true if hash is a proper superset of other_hash, false otherwise:
h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1}
h1 > h2
h2 > h1
h1 > h1
Source
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);
}
Returns true if hash is a superset of other_hash, false otherwise:
h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1}
h1 >= h2
h2 >= h1
h1 >= h1
Source
VALUE
rb_hash_aref(VALUE hash, VALUE key)
{
st_data_t val;
if (hash_stlike_lookup(hash, key, &val)) {
return (VALUE)val;
}
else {
return rb_hash_default_value(hash, key);
}
}
Returns the value associated with the given key, if found:
h = {foo: 0, bar: 1, baz: 2}
h[:foo]
If key is not found, returns a default value (see Default Values):
h = {foo: 0, bar: 1, baz: 2}
h[:nosuch]
Source
VALUE
rb_hash_aset(VALUE hash, VALUE key, VALUE val)
{
bool iter_p = hash_iterating_p(hash);
rb_hash_modify(hash);
if (!RHASH_STRING_KEY_P(hash, key)) {
RHASH_UPDATE_ITER(hash, iter_p, key, hash_aset, val);
}
else {
RHASH_UPDATE_ITER(hash, iter_p, key, hash_aset_str, val);
}
return val;
}
Associates the given value with the given key; returns value.
If the given key exists, replaces its value with the given value; the ordering is not affected (see Entry Order):
h = {foo: 0, bar: 1}
h[:foo] = 2
h.store(:bar, 3)
h
If key does not exist, adds the key and value; the new entry is last in the order (see Entry Order):
h = {foo: 0, bar: 1}
h[:baz] = 2
h.store(:bat, 3)
h
Source
static VALUE
rb_hash_any_p(int argc, VALUE *argv, VALUE hash)
{
VALUE args[2];
args[0] = Qfalse;
rb_check_arity(argc, 0, 1);
if (RHASH_EMPTY_P(hash)) return Qfalse;
if (argc) {
if (rb_block_given_p()) {
rb_warn("given block not used");
}
args[1] = argv[0];
rb_hash_foreach(hash, any_p_i_pattern, (VALUE)args);
}
else {
if (!rb_block_given_p()) {
/* yields pairs, never false */
return Qtrue;
}
if (rb_block_pair_yield_optimizable())
rb_hash_foreach(hash, any_p_i_fast, (VALUE)args);
else
rb_hash_foreach(hash, any_p_i, (VALUE)args);
}
return args[0];
}
Returns true if any element satisfies a given criterion; false otherwise.
If self has no element, returns false and argument or block are not used.
With no argument and no block, returns true if self is non-empty; false if empty.
With argument object and no block, returns true if for any key key h.assoc(key) == object:
h = {foo: 0, bar: 1, baz: 2}
h.any?([:bar, 1])
h.any?([:bar, 0])
h.any?([:baz, 1])
With no argument and a block, calls the block with each key-value pair; returns true if the block returns any truthy value, false otherwise:
h = {foo: 0, bar: 1, baz: 2}
h.any? {|key, value| value < 3 }
h.any? {|key, value| value > 3 }
Related: Enumerable#any?
static VALUE
rb_hash_assoc(VALUE hash, VALUE key)
{
VALUE args[2];
if (RHASH_EMPTY_P(hash)) return Qnil;
if (RHASH_ST_TABLE_P(hash) && !RHASH_IDENTHASH_P(hash)) {
VALUE value = Qundef;
st_table assoctable = *RHASH_ST_TABLE(hash);
assoctable.type = &(struct st_hash_type){
.compare = assoc_cmp,
.hash = assoctable.type->hash,
};
VALUE arg = (VALUE)&(struct assoc_arg){
.tbl = &assoctable,
.key = (st_data_t)key,
};
if (RB_OBJ_FROZEN(hash)) {
value = assoc_lookup(arg);
}
else {
hash_iter_lev_inc(hash);
value = rb_ensure(assoc_lookup, arg, hash_foreach_ensure, hash);
}
hash_verify(hash);
if (!UNDEF_P(value)) return rb_assoc_new(key, value);
}
args[0] = key;
args[1] = Qnil;
rb_hash_foreach(hash, assoc_i, (VALUE)args);
return args[1];
}
If the given key is found, returns a 2-element Array containing that key and its value:
h = {foo: 0, bar: 1, baz: 2}
h.assoc(:bar)
Returns nil if key key is not found.
VALUE
rb_hash_clear(VALUE hash)
{
rb_hash_modify_check(hash);
if (hash_iterating_p(hash)) {
rb_hash_foreach(hash, clear_i, 0);
}
else if (RHASH_AR_TABLE_P(hash)) {
ar_clear(hash);
}
else {
st_clear(RHASH_ST_TABLE(hash));
compact_after_delete(hash);
}
return hash;
}
Removes all hash entries; returns self.
static VALUE
rb_hash_compact(VALUE hash)
{
VALUE result = rb_hash_dup(hash);
if (!RHASH_EMPTY_P(hash)) {
rb_hash_foreach(result, delete_if_nil, result);
compact_after_delete(result);
}
else if (rb_hash_compare_by_id_p(hash)) {
result = rb_hash_compare_by_id(result);
}
return result;
}
Returns a copy of self with all nil-valued entries removed:
h = {foo: 0, bar: nil, baz: 2, bat: nil}
h1 = h.compact
h1
Source
static VALUE
rb_hash_compact_bang(VALUE hash)
{
st_index_t n;
rb_hash_modify_check(hash);
n = RHASH_SIZE(hash);
if (n) {
rb_hash_foreach(hash, delete_if_nil, hash);
if (n != RHASH_SIZE(hash))
return hash;
}
return Qnil;
}
Returns self with all its nil-valued entries removed (in place):
h = {foo: 0, bar: nil, baz: 2, bat: nil}
h.compact!
Returns nil if no entries were removed.
VALUE
rb_hash_compare_by_id(VALUE hash)
{
VALUE tmp;
st_table *identtable;
if (rb_hash_compare_by_id_p(hash)) return hash;
rb_hash_modify_check(hash);
if (hash_iterating_p(hash)) {
rb_raise(rb_eRuntimeError, "compare_by_identity during iteration");
}
if (RHASH_TABLE_EMPTY_P(hash)) {
// Fast path: There's nothing to rehash, so we don't need a `tmp` table.
// We're most likely an AR table, so this will need an allocation.
ar_force_convert_table(hash, __FILE__, __LINE__);
HASH_ASSERT(RHASH_ST_TABLE_P(hash));
RHASH_ST_TABLE(hash)->type = &identhash;
}
else {
// Slow path: Need to rehash the members of `self` into a new
// `tmp` table using the new `identhash` compare/hash functions.
tmp = hash_alloc(0);
hash_st_table_init(tmp, &identhash, RHASH_SIZE(hash));
identtable = RHASH_ST_TABLE(tmp);
rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
rb_hash_free(hash);
// We know for sure `identtable` is an st table,
// so we can skip `ar_force_convert_table` here.
RHASH_ST_TABLE_SET(hash, identtable);
RHASH_ST_CLEAR(tmp);
}
return hash;
}
Sets self to consider only identity in comparing keys; two keys are considered the same only if they are the same object; returns self.
By default, these two object are considered to be the same key, so s1 will overwrite s0:
s0 = 'x'
s1 = 'x'
h = {}
h.compare_by_identity?
h[s0] = 0
h[s1] = 1
h
After calling #compare_by_identity, the keys are considered to be different, and therefore do not overwrite each other:
h = {}
h.compare_by_identity
h.compare_by_identity?
h[s0] = 0
h[s1] = 1
h
Source
VALUE
rb_hash_compare_by_id_p(VALUE hash)
{
return RBOOL(RHASH_IDENTHASH_P(hash));
}
Returns true if compare_by_identity has been called, false otherwise.
static VALUE
rb_hash_default(int argc, VALUE *argv, VALUE hash)
{
VALUE ifnone;
rb_check_arity(argc, 0, 1);
ifnone = RHASH_IFNONE(hash);
if (FL_TEST(hash, RHASH_PROC_DEFAULT)) {
if (argc == 0) return Qnil;
return call_default_proc(ifnone, hash, argv[0]);
}
return ifnone;
}
Returns the default value for the given key. The returned value will be determined either by the default proc or by the default value. See Default Values.
With no argument, returns the current default value:
h = {}
h.default
If key is given, returns the default value for key, regardless of whether that key exists:
h = Hash.new { |hash, key| hash[key] = "No key #{key}"}
h[:foo] = "Hello"
h.default(:foo)
Source
static VALUE
rb_hash_set_default(VALUE hash, VALUE ifnone)
{
rb_hash_modify_check(hash);
SET_DEFAULT(hash, ifnone);
return ifnone;
}
Sets the default value to value; returns value:
h = {}
h.default
h.default = false
h.default
See Default Values.
Sourcestatic VALUE
rb_hash_default_proc(VALUE hash)
{
if (FL_TEST(hash, RHASH_PROC_DEFAULT)) {
return RHASH_IFNONE(hash);
}
return Qnil;
}
Returns the default proc for self (see Default Values):
h = {}
h.default_proc
h.default_proc = proc {|hash, key| "Default value for #{key}" }
h.default_proc.class
Source
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;
}
Sets the default proc for self to proc (see Default Values):
h = {}
h.default_proc
h.default_proc = proc { |hash, key| "Default value for #{key}" }
h.default_proc.class
h.default_proc = nil
h.default_proc
Source
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 (!UNDEF_P(val)) {
compact_after_delete(hash);
return val;
}
else {
if (rb_block_given_p()) {
return rb_yield(key);
}
else {
return Qnil;
}
}
}
Deletes the entry for the given key and returns its associated value.
If no block is given and key is found, deletes the entry and returns the associated value:
h = {foo: 0, bar: 1, baz: 2}
h.delete(:bar)
h
If no block given and key is not found, returns nil.
If a block is given and key is found, ignores the block, deletes the entry, and returns the associated value:
h = {foo: 0, bar: 1, baz: 2}
h.delete(:baz) { |key| raise 'Will never happen'}
h
If a block is given and key is not found, calls the block and returns the blockâs return value:
h = {foo: 0, bar: 1, baz: 2}
h.delete(:nosuch) { |key| "Key #{key} not found" }
h
Source
VALUE
rb_hash_delete_if(VALUE hash)
{
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
rb_hash_modify_check(hash);
if (!RHASH_TABLE_EMPTY_P(hash)) {
rb_hash_foreach(hash, delete_if_i, hash);
compact_after_delete(hash);
}
return hash;
}
If a block given, calls the block with each key-value pair; deletes each entry for which the block returns a truthy value; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.delete_if {|key, value| value > 0 }
If no block given, returns a new Enumerator:
h = {foo: 0, bar: 1, baz: 2}
e = h.delete_if
e.each { |key, value| value > 0 }
Source
static VALUE
rb_hash_dig(int argc, VALUE *argv, VALUE self)
{
rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
self = rb_hash_aref(self, *argv);
if (!--argc) return self;
++argv;
return rb_obj_dig(argc, argv, self, Qnil);
}
Finds and returns the object in nested objects that is specified by key and identifiers. The nested objects may be instances of various classes. See Dig Methods.
Nested Hashes:
h = {foo: {bar: {baz: 2}}}
h.dig(:foo)
h.dig(:foo, :bar)
h.dig(:foo, :bar, :baz)
h.dig(:foo, :bar, :BAZ)
Nested Hashes and Arrays:
h = {foo: {bar: [:a, :b, :c]}}
h.dig(:foo, :bar, 2)
This method will use the default values for keys that are not present:
h = {foo: {bar: [:a, :b, :c]}}
h.dig(:hello)
h.default_proc = -> (hash, _key) { hash }
h.dig(:hello, :world)
h.dig(:hello, :world, :foo, :bar, 2)
Calls the given block with each key-value pair; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.each_pair {|key, value| puts "#{key}: #{value}"}
Output:
foo: 0 bar: 1 baz: 2
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.each_pair
h1 = e.each {|key, value| puts "#{key}: #{value}"}
h1
Output:
foo: 0 bar: 1 baz: 2Source
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;
}
Calls the given block with each key; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.each_key {|key| puts key }
Output:
foo bar baz
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.each_key
h1 = e.each {|key| puts key }
h1
Output:
foo bar bazSource
static VALUE
rb_hash_each_pair(VALUE hash)
{
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
if (rb_block_pair_yield_optimizable())
rb_hash_foreach(hash, each_pair_i_fast, 0);
else
rb_hash_foreach(hash, each_pair_i, 0);
return hash;
}
Calls the given block with each key-value pair; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.each_pair {|key, value| puts "#{key}: #{value}"}
Output:
foo: 0 bar: 1 baz: 2
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.each_pair
h1 = e.each {|key, value| puts "#{key}: #{value}"}
h1
Output:
foo: 0 bar: 1 baz: 2Source
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;
}
Calls the given block with each value; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.each_value {|value| puts value }
Output:
0 1 2
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.each_value
h1 = e.each {|value| puts value }
h1
Output:
0 1 2Source
VALUE
rb_hash_empty_p(VALUE hash)
{
return RBOOL(RHASH_EMPTY_P(hash));
}
Returns true if there are no hash entries, false otherwise:
{}.empty?
{foo: 0, bar: 1, baz: 2}.empty?
Source
static VALUE
rb_hash_eql(VALUE hash1, VALUE hash2)
{
return hash_equal(hash1, hash2, TRUE);
}
Returns true if all of the following are true:
object is a Hash object.
hash and object have the same keys (regardless of order).
For each key key, h[key].eql?(object[key]).
Otherwise, returns false.
h1 = {foo: 0, bar: 1, baz: 2}
h2 = {foo: 0, bar: 1, baz: 2}
h1.eql? h2
h3 = {baz: 2, bar: 1, foo: 0}
h1.eql? h3
Source
static VALUE
rb_hash_except(int argc, VALUE *argv, VALUE hash)
{
int i;
VALUE key, result;
result = hash_dup_with_compare_by_id(hash);
for (i = 0; i < argc; i++) {
key = argv[i];
rb_hash_delete(result, key);
}
compact_after_delete(result);
return result;
}
Returns a new Hash excluding entries for the given keys:
h = { a: 100, b: 200, c: 300 }
h.except(:a)
Any given keys that are not found are ignored.
static VALUE
rb_hash_fetch_m(int argc, VALUE *argv, VALUE hash)
{
VALUE key;
st_data_t val;
long block_given;
rb_check_arity(argc, 1, 2);
key = argv[0];
block_given = rb_block_given_p();
if (block_given && argc == 2) {
rb_warn("block supersedes default value argument");
}
if (hash_stlike_lookup(hash, key, &val)) {
return (VALUE)val;
}
else {
if (block_given) {
return rb_yield(key);
}
else if (argc == 1) {
VALUE desc = rb_protect(rb_inspect, key, 0);
if (NIL_P(desc)) {
desc = rb_any_to_s(key);
}
desc = rb_str_ellipsize(desc, 65);
rb_key_err_raise(rb_sprintf("key not found: %"PRIsVALUE, desc), hash, key);
}
else {
return argv[1];
}
}
}
Returns the value for the given key, if found.
h = {foo: 0, bar: 1, baz: 2}
h.fetch(:bar)
If key is not found and no block was given, returns default_value:
{}.fetch(:nosuch, :default)
If key is not found and a block was given, yields key to the block and returns the blockâs return value:
{}.fetch(:nosuch) {|key| "No key #{key}"}
Raises KeyError if neither default_value nor a block was given.
Note that this method does not use the values of either default or default_proc.
static VALUE
rb_hash_fetch_values(int argc, VALUE *argv, VALUE hash)
{
VALUE result = rb_ary_new2(argc);
long i;
for (i=0; i<argc; i++) {
rb_ary_push(result, rb_hash_fetch(hash, argv[i]));
}
return result;
}
Returns a new Array containing the values associated with the given keys *keys:
h = {foo: 0, bar: 1, baz: 2}
h.fetch_values(:baz, :foo)
Returns a new empty Array if no arguments given.
When a block is given, calls the block with each missing key, treating the blockâs return value as the value for that key:
h = {foo: 0, bar: 1, baz: 2}
values = h.fetch_values(:bar, :foo, :bad, :bam) {|key| key.to_s}
values
When no block is given, raises an exception if any given key is not found.
Sourcestatic 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;
}
Returns a new Array object that is a 1-dimensional flattening of self.
By default, nested Arrays are not flattened:
h = {foo: 0, bar: [:bat, 3], baz: 2}
h.flatten
Takes the depth of recursive flattening from Integer argument level:
h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]}
h.flatten(1)
h.flatten(2)
h.flatten(3)
h.flatten(4)
When level is negative, flattens all nested Arrays:
h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]}
h.flatten(-1)
h.flatten(-2)
When level is zero, returns the equivalent of to_a :
h = {foo: 0, bar: [:bat, 3], baz: 2}
h.flatten(0)
h.flatten(0) == h.to_a
Returns true if key is a key in self, otherwise false.
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];
}
Returns true if value is a value in self, otherwise false.
static VALUE
rb_hash_hash(VALUE hash)
{
st_index_t size = RHASH_SIZE(hash);
st_index_t hval = rb_hash_start(size);
hval = rb_hash_uint(hval, (st_index_t)rb_hash_hash);
if (size) {
rb_hash_foreach(hash, hash_i, (VALUE)&hval);
}
hval = rb_hash_end(hval);
return ST2FIX(hval);
}
Returns the Integer hash-code for the hash.
Two Hash objects have the same hash-code if their content is the same (regardless of order):
h1 = {foo: 0, bar: 1, baz: 2}
h2 = {baz: 2, bar: 1, foo: 0}
h2.hash == h1.hash
h2.eql? h1
Source
VALUE
rb_hash_has_key(VALUE hash, VALUE key)
{
return RBOOL(hash_stlike_lookup(hash, key, NULL));
}
Returns true if key is a key in self, otherwise false.
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);
}
Returns a new String containing the hash entries:
h = {foo: 0, bar: 1, baz: 2}
h.inspect
Source
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;
}
Returns a new Hash object with the each key-value pair inverted:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.invert
h1
Overwrites any repeated new keys: (see Entry Order):
h = {foo: 0, bar: 0, baz: 0}
h.invert
Source
static VALUE
rb_hash_keep_if(VALUE hash)
{
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
rb_hash_modify_check(hash);
if (!RHASH_TABLE_EMPTY_P(hash)) {
rb_hash_foreach(hash, keep_if_i, hash);
}
return hash;
}
Calls the block for each key-value pair; retains the entry if the block returns a truthy value; otherwise deletes the entry; returns self.
h = {foo: 0, bar: 1, baz: 2}
h.keep_if { |key, value| key.start_with?('b') }
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.keep_if
e.each { |key, value| key.start_with?('b') }
Source
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];
}
Returns the key for the first-found entry with the given value (see Entry Order):
h = {foo: 0, bar: 2, baz: 2}
h.key(0)
h.key(2)
Returns nil if no such value is found.
Returns true if key is a key in self, otherwise false.
VALUE
rb_hash_keys(VALUE hash)
{
st_index_t size = RHASH_SIZE(hash);
VALUE keys = rb_ary_new_capa(size);
if (size == 0) return keys;
if (ST_DATA_COMPATIBLE_P(VALUE)) {
RARRAY_PTR_USE(keys, ptr, {
if (RHASH_AR_TABLE_P(hash)) {
size = ar_keys(hash, ptr, size);
}
else {
st_table *table = RHASH_ST_TABLE(hash);
size = st_keys(table, ptr, size);
}
});
rb_gc_writebarrier_remember(keys);
rb_ary_set_len(keys, size);
}
else {
rb_hash_foreach(hash, keys_i, keys);
}
return keys;
}
Returns a new Array containing all keys in self:
h = {foo: 0, bar: 1, baz: 2}
h.keys
Returns the count of entries in self:
{foo: 0, bar: 1, baz: 2}.length
Returns true if key is a key in self, otherwise false.
static VALUE
rb_hash_merge(int argc, VALUE *argv, VALUE self)
{
return rb_hash_update(argc, argv, copy_compare_by_id(rb_hash_dup(self), self));
}
Returns the new Hash formed by merging each of other_hashes into a copy of self.
Each argument in other_hashes must be a Hash.
With arguments and no block:
Returns the new Hash object formed by merging each successive Hash in other_hashes into self.
Each new-key entry is added at the end.
Each duplicate-key entryâs value overwrites the previous value.
Example:
h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h.merge(h1, h2)
With arguments and a block:
Returns a new Hash object that is the merge of self and each given hash.
The given hashes are merged left to right.
Each new-key entry is added at the end.
For each duplicate key:
Calls the block with the key and the old and new values.
The blockâs return value becomes the new value for the entry.
Example:
h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h3 = h.merge(h1, h2) { |key, old_value, new_value| old_value + new_value }
h3
With no arguments:
Returns a copy of self.
The block, if given, is ignored.
Example:
h = {foo: 0, bar: 1, baz: 2}
h.merge
h1 = h.merge { |key, old_value, new_value| raise 'Cannot happen' }
h1
Merges each of other_hashes into self; returns self.
Each argument in other_hashes must be a Hash.
With arguments and no block:
Returns self, after the given hashes are merged into it.
The given hashes are merged left to right.
Each new entry is added at the end.
Each duplicate-key entryâs value overwrites the previous value.
Example:
h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h.merge!(h1, h2)
With arguments and a block:
Returns self, after the given hashes are merged.
The given hashes are merged left to right.
Each new-key entry is added at the end.
For each duplicate key:
Calls the block with the key and the old and new values.
The blockâs return value becomes the new value for the entry.
Example:
h = {foo: 0, bar: 1, baz: 2}
h1 = {bat: 3, bar: 4}
h2 = {bam: 5, bat:6}
h3 = h.merge!(h1, h2) { |key, old_value, new_value| old_value + new_value }
h3
With no arguments:
Returns self, unmodified.
The block, if given, is ignored.
Example:
h = {foo: 0, bar: 1, baz: 2}
h.merge
h1 = h.merge! { |key, old_value, new_value| raise 'Cannot happen' }
h1
Source
static 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];
}
Returns a new 2-element Array consisting of the key and value of the first-found entry whose value is == to value (see Entry Order):
h = {foo: 0, bar: 1, baz: 1}
h.rassoc(1)
Returns nil if no such value found.
VALUE
rb_hash_rehash(VALUE hash)
{
VALUE tmp;
st_table *tbl;
if (hash_iterating_p(hash)) {
rb_raise(rb_eRuntimeError, "rehash during iteration");
}
rb_hash_modify_check(hash);
if (RHASH_AR_TABLE_P(hash)) {
tmp = hash_alloc(0);
rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
hash_ar_free_and_clear_table(hash);
ar_copy(hash, tmp);
}
else if (RHASH_ST_TABLE_P(hash)) {
st_table *old_tab = RHASH_ST_TABLE(hash);
tmp = hash_alloc(0);
hash_st_table_init(tmp, old_tab->type, old_tab->num_entries);
tbl = RHASH_ST_TABLE(tmp);
rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
hash_st_free(hash);
RHASH_ST_TABLE_SET(hash, tbl);
RHASH_ST_CLEAR(tmp);
}
hash_verify(hash);
return hash;
}
Rebuilds the hash table by recomputing the hash index for each key; returns self.
The hash table becomes invalid if the hash value of a key has changed after the entry was created. See Modifying an Active Hash Key.
Sourcestatic VALUE
rb_hash_reject(VALUE hash)
{
VALUE result;
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
result = hash_dup_with_compare_by_id(hash);
if (!RHASH_EMPTY_P(hash)) {
rb_hash_foreach(result, delete_if_i, result);
compact_after_delete(result);
}
return result;
}
Returns a new Hash object whose entries are all those from self for which the block returns false or nil:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.reject {|key, value| key.start_with?('b') }
h1
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.reject
h1 = e.each {|key, value| key.start_with?('b') }
h1
Source
static VALUE
rb_hash_reject_bang(VALUE hash)
{
st_index_t n;
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
rb_hash_modify(hash);
n = RHASH_SIZE(hash);
if (!n) return Qnil;
rb_hash_foreach(hash, delete_if_i, hash);
if (n == RHASH_SIZE(hash)) return Qnil;
return hash;
}
Returns self, whose remaining entries are those for which the block returns false or nil:
h = {foo: 0, bar: 1, baz: 2}
h.reject! {|key, value| value < 2 }
Returns nil if no entries are removed.
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.reject!
e.each {|key, value| key.start_with?('b') }
Replaces the entire contents of self with the contents of other_hash; returns self:
h = {foo: 0, bar: 1, baz: 2}
h.replace({bat: 3, bam: 4})
Source
static VALUE
rb_hash_select(VALUE hash)
{
VALUE result;
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
result = hash_dup_with_compare_by_id(hash);
if (!RHASH_EMPTY_P(hash)) {
rb_hash_foreach(result, keep_if_i, result);
compact_after_delete(result);
}
return result;
}
Returns a new Hash object whose entries are those for which the block returns a truthy value:
h = {foo: 0, bar: 1, baz: 2}
h.select {|key, value| value < 2 }
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.select
e.each {|key, value| value < 2 }
Source
static VALUE
rb_hash_select_bang(VALUE hash)
{
st_index_t n;
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
rb_hash_modify_check(hash);
n = RHASH_SIZE(hash);
if (!n) return Qnil;
rb_hash_foreach(hash, keep_if_i, hash);
if (n == RHASH_SIZE(hash)) return Qnil;
return hash;
}
Returns self, whose entries are those for which the block returns a truthy value:
h = {foo: 0, bar: 1, baz: 2}
h.select! {|key, value| value < 2 } => {:foo=>0, :bar=>1}
Returns nil if no entries were removed.
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.select!
e.each { |key, value| value < 2 }
Source
static VALUE
rb_hash_shift(VALUE hash)
{
struct shift_var var;
rb_hash_modify_check(hash);
if (RHASH_AR_TABLE_P(hash)) {
var.key = Qundef;
if (!hash_iterating_p(hash)) {
if (ar_shift(hash, &var.key, &var.val)) {
return rb_assoc_new(var.key, var.val);
}
}
else {
rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
if (!UNDEF_P(var.key)) {
rb_hash_delete_entry(hash, var.key);
return rb_assoc_new(var.key, var.val);
}
}
}
if (RHASH_ST_TABLE_P(hash)) {
var.key = Qundef;
if (!hash_iterating_p(hash)) {
if (st_shift(RHASH_ST_TABLE(hash), &var.key, &var.val)) {
return rb_assoc_new(var.key, var.val);
}
}
else {
rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
if (!UNDEF_P(var.key)) {
rb_hash_delete_entry(hash, var.key);
return rb_assoc_new(var.key, var.val);
}
}
}
return Qnil;
}
Removes the first hash entry (see Entry Order); returns a 2-element Array containing the removed key and value:
h = {foo: 0, bar: 1, baz: 2}
h.shift
h
Returns nil if the hash is empty.
SourceVALUE
rb_hash_size(VALUE hash)
{
return INT2FIX(RHASH_SIZE(hash));
}
Returns the count of entries in self:
{foo: 0, bar: 1, baz: 2}.length
Source
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 copy_compare_by_id(rb_hash_new(), hash);
}
result = copy_compare_by_id(rb_hash_new_with_size(argc), hash);
for (i = 0; i < argc; i++) {
key = argv[i];
value = rb_hash_lookup2(hash, key, Qundef);
if (!UNDEF_P(value))
rb_hash_aset(result, key, value);
}
return result;
}
Returns a new Hash object containing the entries for the given keys:
h = {foo: 0, bar: 1, baz: 2}
h.slice(:baz, :foo)
Any given keys that are not found are ignored.
Associates the given value with the given key; returns value.
If the given key exists, replaces its value with the given value; the ordering is not affected (see Entry Order):
h = {foo: 0, bar: 1}
h[:foo] = 2
h.store(:bar, 3)
h
If key does not exist, adds the key and value; the new entry is last in the order (see Entry Order):
h = {foo: 0, bar: 1}
h[:baz] = 2
h.store(:bat, 3)
h
Source
static VALUE
rb_hash_to_a(VALUE hash)
{
VALUE ary;
ary = rb_ary_new_capa(RHASH_SIZE(hash));
rb_hash_foreach(hash, to_a_i, ary);
return ary;
}
Returns a new Array of 2-element Array objects; each nested Array contains a key-value pair from self:
h = {foo: 0, bar: 1, baz: 2}
h.to_a
Source
static VALUE
rb_hash_to_h(VALUE hash)
{
if (rb_block_given_p()) {
return rb_hash_to_h_block(hash);
}
if (rb_obj_class(hash) != rb_cHash) {
const VALUE flags = RBASIC(hash)->flags;
hash = hash_dup(hash, rb_cHash, flags & RHASH_PROC_DEFAULT);
}
return hash;
}
For an instance of Hash, returns self.
For a subclass of Hash, returns a new Hash containing the content of self.
When a block is given, returns a new Hash object whose content is based on the block; the block should return a 2-element Array object specifying the key-value pair to be included in the returned Array:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.to_h {|key, value| [value, key] }
h1
Source
static VALUE
rb_hash_to_hash(VALUE hash)
{
return hash;
}
Returns self.
static VALUE
rb_hash_to_proc(VALUE hash)
{
return rb_func_lambda_new(hash_proc_call, hash, 1, 1);
}
Returns a Proc object that maps a key to its value:
h = {foo: 0, bar: 1, baz: 2}
proc = h.to_proc
proc.class
proc.call(:foo)
proc.call(:bar)
proc.call(:nosuch)
Source
static VALUE
rb_hash_transform_keys(int argc, VALUE *argv, VALUE hash)
{
VALUE result;
struct transform_keys_args transarg = {0};
argc = rb_check_arity(argc, 0, 1);
if (argc > 0) {
transarg.trans = to_hash(argv[0]);
transarg.block_given = rb_block_given_p();
}
else {
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
}
result = rb_hash_new();
if (!RHASH_EMPTY_P(hash)) {
if (transarg.trans) {
transarg.result = result;
rb_hash_foreach(hash, transform_keys_hash_i, (VALUE)&transarg);
}
else {
rb_hash_foreach(hash, transform_keys_i, result);
}
}
return result;
}
Returns a new Hash object; each entry has:
A key provided by the block.
The value from self.
An optional hash argument can be provided to map keys to new keys. Any key not given will be mapped using the provided block, or remain the same if no block is given.
Transform keys:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_keys {|key| key.to_s }
h1
h.transform_keys(foo: :bar, bar: :foo)
h.transform_keys(foo: :hello, &:to_s)
Overwrites values for duplicate keys:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_keys {|key| :bat }
h1
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.transform_keys
h1 = e.each { |key| key.to_s }
h1
Source
static VALUE
rb_hash_transform_keys_bang(int argc, VALUE *argv, VALUE hash)
{
VALUE trans = 0;
int block_given = 0;
argc = rb_check_arity(argc, 0, 1);
if (argc > 0) {
trans = to_hash(argv[0]);
block_given = rb_block_given_p();
}
else {
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
}
rb_hash_modify_check(hash);
if (!RHASH_TABLE_EMPTY_P(hash)) {
long i;
VALUE new_keys = hash_alloc(0);
VALUE pairs = rb_ary_hidden_new(RHASH_SIZE(hash) * 2);
rb_hash_foreach(hash, flatten_i, pairs);
for (i = 0; i < RARRAY_LEN(pairs); i += 2) {
VALUE key = RARRAY_AREF(pairs, i), new_key, val;
if (!trans) {
new_key = rb_yield(key);
}
else if (!UNDEF_P(new_key = rb_hash_lookup2(trans, key, Qundef))) {
/* use the transformed key */
}
else if (block_given) {
new_key = rb_yield(key);
}
else {
new_key = key;
}
val = RARRAY_AREF(pairs, i+1);
if (!hash_stlike_lookup(new_keys, key, NULL)) {
rb_hash_stlike_delete(hash, &key, NULL);
}
rb_hash_aset(hash, new_key, val);
rb_hash_aset(new_keys, new_key, Qnil);
}
rb_ary_clear(pairs);
rb_hash_clear(new_keys);
}
compact_after_delete(hash);
return hash;
}
Same as Hash#transform_keys but modifies the receiver in place instead of returning a new hash.
static VALUE
rb_hash_transform_values(VALUE hash)
{
VALUE result;
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
result = hash_dup_with_compare_by_id(hash);
SET_DEFAULT(result, Qnil);
if (!RHASH_EMPTY_P(hash)) {
rb_hash_stlike_foreach_with_replace(result, transform_values_foreach_func, transform_values_foreach_replace, result);
compact_after_delete(result);
}
return result;
}
Returns a new Hash object; each entry has:
A key from self.
A value provided by the block.
Transform values:
h = {foo: 0, bar: 1, baz: 2}
h1 = h.transform_values {|value| value * 100}
h1
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.transform_values
h1 = e.each { |value| value * 100}
h1
Source
static VALUE
rb_hash_transform_values_bang(VALUE hash)
{
RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
rb_hash_modify_check(hash);
if (!RHASH_TABLE_EMPTY_P(hash)) {
rb_hash_stlike_foreach_with_replace(hash, transform_values_foreach_func, transform_values_foreach_replace, hash);
}
return hash;
}
Returns self, whose keys are unchanged, and whose values are determined by the given block.
h = {foo: 0, bar: 1, baz: 2}
h.transform_values! {|value| value * 100}
Returns a new Enumerator if no block given:
h = {foo: 0, bar: 1, baz: 2}
e = h.transform_values!
h1 = e.each {|value| value * 100}
h1
Returns true if value is a value in self, otherwise false.
VALUE
rb_hash_values(VALUE hash)
{
VALUE values;
st_index_t size = RHASH_SIZE(hash);
values = rb_ary_new_capa(size);
if (size == 0) return values;
if (ST_DATA_COMPATIBLE_P(VALUE)) {
if (RHASH_AR_TABLE_P(hash)) {
rb_gc_writebarrier_remember(values);
RARRAY_PTR_USE(values, ptr, {
size = ar_values(hash, ptr, size);
});
}
else if (RHASH_ST_TABLE_P(hash)) {
st_table *table = RHASH_ST_TABLE(hash);
rb_gc_writebarrier_remember(values);
RARRAY_PTR_USE(values, ptr, {
size = st_values(table, ptr, size);
});
}
rb_ary_set_len(values, size);
}
else {
rb_hash_foreach(hash, values_i, values);
}
return values;
}
Returns a new Array containing all values in self:
h = {foo: 0, bar: 1, baz: 2}
h.values
Source
static 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;
}
Returns a new Array containing values for the given keys:
h = {foo: 0, bar: 1, baz: 2}
h.values_at(:baz, :foo)
The default values are returned for any keys that are not found:
h.values_at(:hello, :foo)
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