class Hash
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 “hash rocket,” =>
:
h = {:foo => 0, :bar => 1, :baz => 2} h # => {:foo=>0, :bar=>1, :baz=>2}
Alternatively, but only for a Hash key that’s a Symbol
, you can use a newer JSON-style syntax, where each bareword becomes a Symbol:
h = {foo: 0, bar: 1, baz: 2} h # => {:foo=>0, :bar=>1, :baz=>2}
You can also use a String
in place of a bareword:
h = {'foo': 0, 'bar': 1, 'baz': 2} h # => {:foo=>0, :bar=>1, :baz=>2}
And you can mix the styles:
h = {foo: 0, :bar => 1, 'baz': 2} h # => {:foo=>0, :bar=>1, :baz=>2}
But it’s an error to try the JSON-style syntax for a key that’s 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 # => {:x=>0, :y=>100}
Common Uses¶ ↑
You can use a Hash to give names to objects:
person = {name: 'Matz', language: 'Ruby'} person # => {:name=>"Matz", :language=>"Ruby"}
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}) # => {: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) # => {: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 # => #<Dev: @name="Matz", @language="Ruby">
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 # => Hash
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 # => {:foo=>0, :bar=>1, :baz=>2}
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 # => {:foo=>0, :bar=>1, :baz=>2}
Hash Value Basics¶ ↑
The simplest way to retrieve a Hash value (instance method []
):
h = {foo: 0, bar: 1, baz: 2} h[:foo] # => 0
The simplest way to create or update a Hash value (instance method []=
):
h = {foo: 0, bar: 1, baz: 2} h[:bat] = 3 # => 3 h # => {:foo=>0, :bar=>1, :baz=>2, :bat=>3} h[:foo] = 4 # => 4 h # => {:foo=>4, :bar=>1, :baz=>2, :bat=>3}
The simplest way to delete a Hash entry (instance method delete
):
h = {foo: 0, bar: 1, baz: 2} h.delete(:bar) # => 1 h # => {:foo=>0, :baz=>2}
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 methodinspect
.
A new Hash has its initial ordering per the given entries:
h = Hash[foo: 0, bar: 1] h # => {:foo=>0, :bar=>1}
New entries are added at the end:
h[:baz] = 2 h # => {:foo=>0, :bar=>1, :baz=>2}
Updating a value does not affect the order:
h[:baz] = 3 h # => {:foo=>0, :bar=>1, :baz=>3}
But re-creating a deleted entry can affect the order:
h.delete(:foo) h[:foo] = 5 h # => {:bar=>1, :baz=>3, :foo=>5}
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.
Modifying an Active Hash Key¶ ↑
Modifying a Hash key while it is in use damages the hash’s index.
This Hash has keys that are Arrays:
a0 = [ :foo, :bar ] a1 = [ :baz, :bat ] h = {a0 => 0, a1 => 1} h.include?(a0) # => true h[a0] # => 0 a0.hash # => 110002110
Modifying array element a0[0]
changes its hash value:
a0[0] = :bam a0.hash # => 1069447059
And damages the Hash index:
h.include?(a0) # => false h[a0] # => nil
You can repair the hash index using method rehash
:
h.rehash # => {[:bam, :bar]=>0, [:baz, :bat]=>1} h.include?(a0) # => true h[a0] # => 0
A String
key is always safe. That’s because an unfrozen String
passed as a key will be replaced by a duplicated and frozen String:
s = 'foo' s.frozen? # => false h = {s => 0} first_key = h.keys.first first_key.frozen? # => true
User-Defined Hash Keys¶ ↑
To be useable 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 keys’ 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 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 && 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 #=> 1
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 ‘nil`).
You can retrieve the default value with method default
:
h = Hash.new h.default # => nil
You can set the default value by passing an argument to method Hash.new
or with method default=
h = Hash.new(-1) h.default # => -1 h.default = 0 h.default # => 0
This default value is returned for []
, values_at
and dig
when a key is not found:
counts = {foo: 42} counts.default # => nil (default) counts[:foo] = 42 counts[:bar] # => nil counts.default = 0 counts[:bar] # => 0 counts.values_at(:foo, :bar, :baz) # => [42, 0, 0] counts.dig(:bar) # => 0
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 # => [:hi], but this mutates the default! synonyms.default # => [:hi] synonyms[:world] << :universe synonyms[:world] # => [:hi, :universe], oops synonyms.keys # => [], oops
To use a mutable object as default, it is recommended to use a default proc
Default Proc
¶ ↑
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 # => nil
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 # => Proc h.default_proc = proc { |hash, key| "Default value for #{key.inspect}" } h.default_proc.class # => Proc
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 proc’s return value:
h = Hash.new { |hash, key| "Default value for #{key}" } h[:nosuch] # => "Default value for nosuch"
Note that in the example above no entry for key :nosuch
is created:
h.include?(:nosuch) # => false
However, the proc itself can add a new entry:
synonyms = Hash.new { |hash, key| hash[key] = [] } synonyms.include?(:hello) # => false synonyms[:hello] << :hi # => [:hi] synonyms[:world] << :universe # => [:universe] synonyms.keys # => [:hello, :world]
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.
What’s Here¶ ↑
First, what’s 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
.
Methods for Creating a 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.
Methods for Setting Hash State¶ ↑
-
compare_by_identity
: Setsself
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.
Methods for Querying¶ ↑
-
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 toself
. -
hash
: Returns the integer hash code. -
has_value?
: Returns whether a given object is a value inself
. -
include?
,has_key?
,member?
,key?
: Returns whether a given object is a key inself
. -
value?
: Returns whether a given object is a value inself
.
Methods for Comparing¶ ↑
-
#<: 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 toself
. -
#>: Returns whether
self
is a proper superset of a given object -
#>=: Returns whether
self
is a superset of a given object.
Methods for Fetching¶ ↑
-
[]
: 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 inself
. -
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 inself
/ -
values_at
: Returns an array containing values for given keys.
Methods for Assigning¶ ↑
-
merge
: Returns the hash formed by merging each given hash into a copy ofself
. -
replace
: Replaces the entire contents ofself
with the contents of a given hash.
Methods for Deleting¶ ↑
These methods remove entries from self
:
-
clear
: Removes all entries fromself
. -
compact!
: Removes allnil
-valued entries fromself
. -
delete
: Removes the entry for a given key. -
delete_if
: Removes entries selected by a given block. -
filter!
,select!
: 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 ofself
with allnil
-valued entries removed. -
except
: Returns a copy ofself
with entries removed for specified keys. -
filter
,select
: Returns a copy ofself
with only those entries selected by a given block. -
reject
: Returns a copy ofself
with entries removed as specified by a given block. -
slice
: Returns a hash containing the entries for given keys.
Methods for Iterating¶ ↑
-
each
,each_pair
: 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.
Methods for Converting¶ ↑
-
inspect
,to_s
: Returns a newString
containing the hash entries. -
to_a
: Returns a new array of 2-element arrays; each nested array contains a key-value pair fromself
. -
to_h
: Returnsself
if a Hash; if a subclass of Hash, returns a Hash containing the entries fromself
. -
to_hash
: Returnsself
. -
to_proc
: Returns a proc that maps a given key to its value.
Methods for Transforming Keys and Values¶ ↑
-
transform_keys
: Returns a copy ofself
with modified keys. -
transform_keys!
: Modifies keys inself
-
transform_values
: Returns a copy ofself
with modified values. -
transform_values!
: Modifies values inself
.
Other Methods¶ ↑
Public Class Methods
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] # => {:foo=>0, :bar=>1, :baz=>2}
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] ] ] # => {: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] # => {:foo=>0, :bar=>1}
Raises an exception if the argument list does not conform to any of the above.
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 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 given, initializes both the default value and the default proc to nil
:
h = Hash.new h.default # => nil h.default_proc # => nil
If argument default_value
given but no block given, initializes the default value to the given default_value
and the default proc to nil
:
h = Hash.new(false) h.default # => false h.default_proc # => nil
If a block given but no argument, 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 # => nil h.default_proc.class # => Proc h[:nosuch] # => "Default value for nosuch"
static VALUE rb_hash_initialize(int argc, VALUE *argv, VALUE hash) { rb_hash_modify(hash); if (rb_block_given_p()) { rb_check_arity(argc, 0, 0); SET_PROC_DEFAULT(hash, rb_block_proc()); } else { rb_check_arity(argc, 0, 1); VALUE options, ifnone; rb_scan_args(argc, argv, "01:", &ifnone, &options); if (NIL_P(ifnone) && !NIL_P(options)) { ifnone = options; rb_warn_deprecated_to_remove("3.4", "Calling Hash.new with keyword arguments", "Hash.new({ key: value })"); } RHASH_SET_IFNONE(hash, ifnone); } return hash; }
Duplicates a given hash and adds a ruby2_keywords flag. This method is not for casual use; debugging, researching, and some truly necessary cases like deserialization of arguments.
h = {k: 1} h = Hash.ruby2_keywords_hash(h) def foo(k: 42) k end foo(*[h]) #=> 1 with neither a warning or an error
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; }
Checks if a given hash is flagged by Module#ruby2_keywords
(or Proc#ruby2_keywords
). This method is not for casual use; debugging, researching, and some truly necessary cases like serialization of arguments.
ruby2_keywords def foo(*args) Hash.ruby2_keywords_hash?(args.last) end foo(k: 1) #=> true foo({k: 1}) #=> false
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); }
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_s_try_convert(VALUE dummy, VALUE hash) { return rb_check_hash_type(hash); }
Public Instance Methods
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 # => true h2 < h1 # => false h1 < h1 # => false
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 subset of other_hash
, false
otherwise:
h1 = {foo: 0, bar: 1} h2 = {foo: 0, bar: 1, baz: 2} h1 <= h2 # => true h2 <= h1 # => false h1 <= h1 # => true
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 all of the following are true:
-
object
is a Hash object. -
hash
andobject
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 # => true h3 = {baz: 2, bar: 1, foo: 0} h1 == h3 # => true
static VALUE rb_hash_equal(VALUE hash1, VALUE hash2) { return hash_equal(hash1, hash2, FALSE); }
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 # => true h2 > h1 # => false h1 > h1 # => false
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 superset of other_hash
, false
otherwise:
h1 = {foo: 0, bar: 1, baz: 2} h2 = {foo: 0, bar: 1} h1 >= h2 # => true h2 >= h1 # => false h1 >= h1 # => true
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 the value associated with the given key
, if found:
h = {foo: 0, bar: 1, baz: 2} h[:foo] # => 0
If key
is not found, returns a default value (see Default Values):
h = {foo: 0, bar: 1, baz: 2} h[:nosuch] # => nil
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); } }
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 # => 2 h.store(:bar, 3) # => 3 h # => {:foo=>2, :bar=>3}
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 # => 2 h.store(:bat, 3) # => 3 h # => {:foo=>0, :bar=>1, :baz=>2, :bat=>3}
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; }
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]) # => true h.any?([:bar, 0]) # => false h.any?([:baz, 1]) # => false
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 } # => true h.any? {|key, value| value > 3 } # => false
Related: Enumerable#any?
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]; }
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) # => [:bar, 1]
Returns nil
if key key
is not found.
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]; }
Removes all hash entries; returns self
.
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; }
Returns a copy of self
with all nil
-valued entries removed:
h = {foo: 0, bar: nil, baz: 2, bat: nil} h1 = h.compact h1 # => {:foo=>0, :baz=>2}
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 self
with all its nil
-valued entries removed (in place):
h = {foo: 0, bar: nil, baz: 2, bat: nil} h.compact! # => {:foo=>0, :baz=>2}
Returns nil
if no entries were removed.
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; }
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? # => false h[s0] = 0 h[s1] = 1 h # => {"x"=>1}
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? # => true h[s0] = 0 h[s1] = 1 h # => {"x"=>0, "x"=>1}
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; }
Returns true
if compare_by_identity
has been called, false
otherwise.
VALUE rb_hash_compare_by_id_p(VALUE hash) { return RBOOL(RHASH_IDENTHASH_P(hash)); }
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 # => nil
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) # => "No key foo"
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; }
Sets the default value to value
; returns value
:
h = {} h.default # => nil h.default = false # => false h.default # => false
See Default Values.
static VALUE rb_hash_set_default(VALUE hash, VALUE ifnone) { rb_hash_modify_check(hash); SET_DEFAULT(hash, ifnone); return ifnone; }
Returns the default proc for self
(see Default Values):
h = {} h.default_proc # => nil h.default_proc = proc {|hash, key| "Default value for #{key}" } h.default_proc.class # => Proc
static VALUE rb_hash_default_proc(VALUE hash) { if (FL_TEST(hash, RHASH_PROC_DEFAULT)) { return RHASH_IFNONE(hash); } return Qnil; }
Sets the default proc for self
to proc
: (see Default Values):
h = {} h.default_proc # => nil h.default_proc = proc { |hash, key| "Default value for #{key}" } h.default_proc.class # => Proc h.default_proc = nil h.default_proc # => nil
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; }
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) # => 1 h # => {:foo=>0, :baz=>2}
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'} # => 2 h # => {:foo=>0, :bar=>1}
If a block is given and key
is not found, calls the block and returns the block’s return value:
h = {foo: 0, bar: 1, baz: 2} h.delete(:nosuch) { |key| "Key #{key} not found" } # => "Key nosuch not found" h # => {:foo=>0, :bar=>1, :baz=>2}
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; } } }
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 } # => {:foo=>0}
If no block given, returns a new Enumerator:
h = {foo: 0, bar: 1, baz: 2} e = h.delete_if # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:delete_if> e.each { |key, value| value > 0 } # => {:foo=>0}
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; }
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) # => {:bar=>{:baz=>2}} h.dig(:foo, :bar) # => {:baz=>2} h.dig(:foo, :bar, :baz) # => 2 h.dig(:foo, :bar, :BAZ) # => nil
Nested Hashes and Arrays:
h = {foo: {bar: [:a, :b, :c]}} h.dig(:foo, :bar, 2) # => :c
This method will use the default values for keys that are not present:
h = {foo: {bar: [:a, :b, :c]}} h.dig(:hello) # => nil h.default_proc = -> (hash, _key) { hash } h.dig(:hello, :world) # => h h.dig(:hello, :world, :foo, :bar, 2) # => :c
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); }
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}"} # => {:foo=>0, :bar=>1, :baz=>2}
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 # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_pair> h1 = e.each {|key, value| puts "#{key}: #{value}"} h1 # => {:foo=>0, :bar=>1, :baz=>2}
Output:
foo: 0 bar: 1 baz: 2
Calls the given block with each key; returns self
:
h = {foo: 0, bar: 1, baz: 2} h.each_key {|key| puts key } # => {:foo=>0, :bar=>1, :baz=>2}
Output:
foo bar baz
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.each_key # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_key> h1 = e.each {|key| puts key } h1 # => {:foo=>0, :bar=>1, :baz=>2}
Output:
foo bar baz
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-value pair; returns self
:
h = {foo: 0, bar: 1, baz: 2} h.each_pair {|key, value| puts "#{key}: #{value}"} # => {:foo=>0, :bar=>1, :baz=>2}
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 # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_pair> h1 = e.each {|key, value| puts "#{key}: #{value}"} h1 # => {:foo=>0, :bar=>1, :baz=>2}
Output:
foo: 0 bar: 1 baz: 2
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 value; returns self
:
h = {foo: 0, bar: 1, baz: 2} h.each_value {|value| puts value } # => {:foo=>0, :bar=>1, :baz=>2}
Output:
0 1 2
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.each_value # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:each_value> h1 = e.each {|value| puts value } h1 # => {:foo=>0, :bar=>1, :baz=>2}
Output:
0 1 2
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; }
Returns true
if there are no hash entries, false
otherwise:
{}.empty? # => true {foo: 0, bar: 1, baz: 2}.empty? # => false
static VALUE rb_hash_empty_p(VALUE hash) { return RBOOL(RHASH_EMPTY_P(hash)); }
Returns true
if all of the following are true:
-
object
is a Hash object. -
hash
andobject
have the same keys (regardless of order). -
For each key
key
,h[key] eql? object[key]
.
Otherwise, returns false
.
Equal:
h1 = {foo: 0, bar: 1, baz: 2} h2 = {foo: 0, bar: 1, baz: 2} h1.eql? h2 # => true h3 = {baz: 2, bar: 1, foo: 0} h1.eql? h3 # => true
static VALUE rb_hash_eql(VALUE hash1, VALUE hash2) { return hash_equal(hash1, hash2, TRUE); }
Returns a new Hash excluding entries for the given keys
:
h = { a: 100, b: 200, c: 300 } h.except(:a) #=> {:b=>200, :c=>300}
Any given keys
that are not found are ignored.
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 the value for the given key
, if found.
h = {foo: 0, bar: 1, baz: 2} h.fetch(:bar) # => 1
If key
is not found and no block was given, returns default_value
:
{}.fetch(:nosuch, :default) # => :default
If key
is not found and a block was given, yields key
to the block and returns the block’s return value:
{}.fetch(:nosuch) {|key| "No key #{key}"} # => "No key nosuch"
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_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 a new Array
containing the values associated with the given keys *keys:
h = {foo: 0, bar: 1, baz: 2} h.fetch_values(:baz, :foo) # => [2, 0]
Returns a new empty Array
if no arguments given.
When a block is given, calls the block with each missing key, treating the block’s 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 # => [1, 0, "bad", "bam"]
When no block is given, raises an exception if any given key is not found.
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 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 } # => {:foo=>0, :bar=>1}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.select # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select> e.each {|key, value| value < 2 } # => {:foo=>0, :bar=>1}
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! # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select!> e.each { |key, value| value < 2 } # => {:foo=>0, :bar=>1}
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 # => [:foo, 0, :bar, [:bat, 3], :baz, 2]
Takes the depth of recursive flattening from Integer
argument level
:
h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]} h.flatten(1) # => [:foo, 0, :bar, [:bat, [:baz, [:bat]]]] h.flatten(2) # => [:foo, 0, :bar, :bat, [:baz, [:bat]]] h.flatten(3) # => [:foo, 0, :bar, :bat, :baz, [:bat]] h.flatten(4) # => [:foo, 0, :bar, :bat, :baz, :bat]
When level
is negative, flattens all nested Arrays:
h = {foo: 0, bar: [:bat, [:baz, [:bat, ]]]} h.flatten(-1) # => [:foo, 0, :bar, :bat, :baz, :bat] h.flatten(-2) # => [:foo, 0, :bar, :bat, :baz, :bat]
When level
is zero, returns the equivalent of to_a
:
h = {foo: 0, bar: [:bat, 3], baz: 2} h.flatten(0) # => [[:foo, 0], [:bar, [:bat, 3]], [:baz, 2]] h.flatten(0) == h.to_a # => true
static VALUE rb_hash_flatten(int argc, VALUE *argv, VALUE hash) { VALUE ary; rb_check_arity(argc, 0, 1); if (argc) { int level = NUM2INT(argv[0]); if (level == 0) return rb_hash_to_a(hash); ary = rb_ary_new_capa(RHASH_SIZE(hash) * 2); rb_hash_foreach(hash, flatten_i, ary); level--; if (level > 0) { VALUE ary_flatten_level = INT2FIX(level); rb_funcallv(ary, id_flatten_bang, 1, &ary_flatten_level); } else if (level < 0) { /* flatten recursively */ rb_funcallv(ary, id_flatten_bang, 0, 0); } } else { ary = rb_ary_new_capa(RHASH_SIZE(hash) * 2); rb_hash_foreach(hash, flatten_i, ary); } return ary; }
Returns true
if key
is a key in self
, otherwise false
.
Returns true
if value
is a value 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 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 # => true h2.eql? h1 # => true
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 true
if key
is a key in self
, otherwise false
.
VALUE rb_hash_has_key(VALUE hash, VALUE key) { return RBOOL(hash_stlike_lookup(hash, key, NULL)); }
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}) # => {:bat=>3, :bam=>4}
static VALUE rb_hash_replace(VALUE hash, VALUE hash2) { rb_hash_modify_check(hash); if (hash == hash2) return hash; if (hash_iterating_p(hash)) { rb_raise(rb_eRuntimeError, "can't replace hash during iteration"); } hash2 = to_hash(hash2); COPY_DEFAULT(hash, hash2); if (RHASH_AR_TABLE_P(hash)) { hash_ar_free_and_clear_table(hash); } else { hash_st_free_and_clear_table(hash); } hash_copy(hash, hash2); return hash; }
Returns a new String
containing the hash entries:
h = {foo: 0, bar: 1, baz: 2} h.inspect # => "{:foo=>0, :bar=>1, :baz=>2}"
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 Hash object with the each key-value pair inverted:
h = {foo: 0, bar: 1, baz: 2} h1 = h.invert h1 # => {0=>:foo, 1=>:bar, 2=>:baz}
Overwrites any repeated new keys: (see Entry Order):
h = {foo: 0, bar: 0, baz: 0} h.invert # => {0=>:baz}
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; }
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') } # => {:bar=>1, :baz=>2}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.keep_if # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:keep_if> e.each { |key, value| key.start_with?('b') } # => {:bar=>1, :baz=>2}
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; }
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) # => :foo h.key(2) # => :bar
Returns nil
if no such value is found.
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 true
if key
is a key in self
, otherwise false
.
Returns a new Array
containing all keys in self
:
h = {foo: 0, bar: 1, baz: 2} h.keys # => [:foo, :bar, :baz]
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 the count of entries in self
:
{foo: 0, bar: 1, baz: 2}.length # => 3
Returns true
if key
is a key in self
, otherwise false
.
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
intoself
. -
Each new-key entry is added at the end.
-
Each duplicate-key entry’s 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) # => {:foo=>0, :bar=>4, :baz=>2, :bat=>6, :bam=>5}
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 block’s 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 # => {:foo=>0, :bar=>5, :baz=>2, :bat=>9, :bam=>5}
With no arguments:
-
Returns a copy of
self
. -
The block, if given, is ignored.
Example:
h = {foo: 0, bar: 1, baz: 2} h.merge # => {:foo=>0, :bar=>1, :baz=>2} h1 = h.merge { |key, old_value, new_value| raise 'Cannot happen' } h1 # => {:foo=>0, :bar=>1, :baz=>2}
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)); }
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 entry’s 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) # => {:foo=>0, :bar=>4, :baz=>2, :bat=>6, :bam=>5}
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 block’s 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 # => {:foo=>0, :bar=>5, :baz=>2, :bat=>9, :bam=>5}
With no arguments:
-
Returns
self
, unmodified. -
The block, if given, is ignored.
Example:
h = {foo: 0, bar: 1, baz: 2} h.merge # => {:foo=>0, :bar=>1, :baz=>2} h1 = h.merge! { |key, old_value, new_value| raise 'Cannot happen' } h1 # => {:foo=>0, :bar=>1, :baz=>2}
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) # => [:bar, 1]
Returns nil
if no such value found.
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]; }
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.
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; }
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 # => {:foo=>0}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.reject # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:reject> h1 = e.each {|key, value| key.start_with?('b') } h1 # => {:foo=>0}
static 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 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 } # => {:baz=>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! # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:reject!> e.each {|key, value| key.start_with?('b') } # => {:foo=>0}
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; }
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}) # => {:bat=>3, :bam=>4}
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 } # => {:foo=>0, :bar=>1}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.select # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select> e.each {|key, value| value < 2 } # => {:foo=>0, :bar=>1}
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 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! # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:select!> e.each { |key, value| value < 2 } # => {:foo=>0, :bar=>1}
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; }
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 # => [:foo, 0] h # => {:bar=>1, :baz=>2}
Returns nil if the hash is empty.
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; }
Returns the count of entries in self
:
{foo: 0, bar: 1, baz: 2}.length # => 3
VALUE rb_hash_size(VALUE hash) { return INT2FIX(RHASH_SIZE(hash)); }
Returns a new Hash object containing the entries for the given keys
:
h = {foo: 0, bar: 1, baz: 2} h.slice(:baz, :foo) # => {:baz=>2, :foo=>0}
Any given keys
that are not found are ignored.
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; }
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 # => 2 h.store(:bar, 3) # => 3 h # => {:foo=>2, :bar=>3}
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 # => 2 h.store(:bat, 3) # => 3 h # => {:foo=>0, :bar=>1, :baz=>2, :bat=>3}
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 # => [[:foo, 0], [:bar, 1], [:baz, 2]]
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; }
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 # => {0=>:foo, 1=>:bar, 2=>:baz}
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; }
Returns self
.
static VALUE rb_hash_to_hash(VALUE hash) { return hash; }
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 proc.call(:foo) # => 0 proc.call(:bar) # => 1 proc.call(:nosuch) # => nil
static VALUE rb_hash_to_proc(VALUE hash) { return rb_func_lambda_new(hash_proc_call, hash, 1, 1); }
Returns a new String
containing the hash entries:
h = {foo: 0, bar: 1, baz: 2} h.inspect # => "{:foo=>0, :bar=>1, :baz=>2}"
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 # => {"foo"=>0, "bar"=>1, "baz"=>2} h.transform_keys(foo: :bar, bar: :foo) #=> {bar: 0, foo: 1, baz: 2} h.transform_keys(foo: :hello, &:to_s) #=> {:hello=>0, "bar"=>1, "baz"=>2}
Overwrites values for duplicate keys:
h = {foo: 0, bar: 1, baz: 2} h1 = h.transform_keys {|key| :bat } h1 # => {:bat=>2}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.transform_keys # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:transform_keys> h1 = e.each { |key| key.to_s } h1 # => {"foo"=>0, "bar"=>1, "baz"=>2}
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; }
Same as Hash#transform_keys
but modifies the receiver in place instead of returning a new hash.
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; }
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 # => {:foo=>0, :bar=>100, :baz=>200}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.transform_values # => #<Enumerator: {:foo=>0, :bar=>1, :baz=>2}:transform_values> h1 = e.each { |value| value * 100} h1 # => {:foo=>0, :bar=>100, :baz=>200}
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 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} # => {:foo=>0, :bar=>100, :baz=>200}
Returns a new Enumerator
if no block given:
h = {foo: 0, bar: 1, baz: 2} e = h.transform_values! # => #<Enumerator: {:foo=>0, :bar=>100, :baz=>200}:transform_values!> h1 = e.each {|value| value * 100} h1 # => {:foo=>0, :bar=>100, :baz=>200}
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; }
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 entry’s 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) # => {:foo=>0, :bar=>4, :baz=>2, :bat=>6, :bam=>5}
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 block’s 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 # => {:foo=>0, :bar=>5, :baz=>2, :bat=>9, :bam=>5}
With no arguments:
-
Returns
self
, unmodified. -
The block, if given, is ignored.
Example:
h = {foo: 0, bar: 1, baz: 2} h.merge # => {:foo=>0, :bar=>1, :baz=>2} h1 = h.merge! { |key, old_value, new_value| raise 'Cannot happen' } h1 # => {:foo=>0, :bar=>1, :baz=>2}
static VALUE rb_hash_update(int argc, VALUE *argv, VALUE self) { int i; bool block_given = rb_block_given_p(); rb_hash_modify(self); for (i = 0; i < argc; i++){ VALUE hash = to_hash(argv[i]); if (block_given) { rb_hash_foreach(hash, rb_hash_update_block_i, self); } else { rb_hash_foreach(hash, rb_hash_update_i, self); } } return self; }
Returns true
if value
is a value in self
, otherwise false
.
Returns a new Array
containing all values in self
:
h = {foo: 0, bar: 1, baz: 2} h.values # => [0, 1, 2]
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 values for the given keys
:
h = {foo: 0, bar: 1, baz: 2} h.values_at(:baz, :foo) # => [2, 0]
The default values are returned for any keys that are not found:
h.values_at(:hello, :foo) # => [nil, 0]
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; }