class Hash(K, V)

Overview

A Hash represents a mapping of keys to values.

See the official docs for the basics.

Included Modules

Defined in:

hash.cr
json/to_json.cr
yaml/to_yaml.cr

Class Method Summary

Instance Method Summary

Instance methods inherited from module Iterable({K, V})

chunk(reuse = false, &block : {K, V} -> U) forall U chunk, cycle(n)
cycle cycle, each each, each_cons(count : Int, reuse = false) each_cons, each_slice(count : Int, reuse = false) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object

Instance methods inherited from module Enumerable({K, V})

all?(&block)
all? all?, any?(&block)
any? any?, chunks(&block : {K, V} -> U) forall U chunks, compact_map(&block) compact_map, count(&block)
count(item) count, cycle(n, &block)
cycle(&block) cycle, each(&block : {K, V} -> _) each, each_cons(count : Int, reuse = false, &block) each_cons, each_slice(count : Int, reuse = false, &block) each_slice, each_with_index(offset = 0, &block) each_with_index, each_with_object(obj, &block) each_with_object, find(if_none = nil, &block) find, first(count : Int)
first first, first? first?, flat_map(&block : {K, V} -> Array(U) | U) forall U flat_map, grep(pattern) grep, group_by(&block : {K, V} -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &block) forall U in_groups_of, includes?(obj) includes?, index(&block)
index(obj) index, index_by(&block : {K, V} -> U) forall U index_by, join(separator, io)
join(separator = "")
join(separator, io, &block)
join(separator = "", &block) join, map(&block : {K, V} -> U) forall U map, map_with_index(&block : {K, V}, Int32 -> U) map_with_index, max max, max? max?, max_by(&block : {K, V} -> U) forall U max_by, max_by?(&block : {K, V} -> U) forall U max_by?, max_of(&block : {K, V} -> U) forall U max_of, max_of?(&block : {K, V} -> U) forall U max_of?, min min, min? min?, min_by(&block : {K, V} -> U) forall U min_by, min_by?(&block : {K, V} -> U) forall U min_by?, min_of(&block : {K, V} -> U) forall U min_of, min_of?(&block : {K, V} -> U) forall U min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : {K, V} -> U) forall U minmax_by, minmax_by?(&block : {K, V} -> U) forall U minmax_by?, minmax_of(&block : {K, V} -> U) forall U minmax_of, minmax_of?(&block : {K, V} -> U) forall U minmax_of?, none?(&block)
none? none?, one?(&block) one?, partition(&block) partition, product(&block)
product(initial : Number, &block)
product
product(initial : Number) product, reduce(&block)
reduce(memo, &block) reduce, reject(&block : {K, V} -> ) reject, select(&block : {K, V} -> ) select, size size, skip(count : Int) skip, skip_while(&block) skip_while, sum(initial)
sum
sum(initial, &block)
sum(&block) sum, take_while(&block) take_while, to_a to_a, to_h to_h, to_set to_set

Instance methods inherited from class Reference

==(other : self)
==(other) ==, dup dup, hash hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference)
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

Class methods inherited from class Reference

new new

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, class class, dup dup, hash hash, inspect(io : IO)
inspect inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&block) tap, to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s
to_s(io : IO) to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&block) try

Class methods inherited from class Object

==(other : Class) ==, ===(other) ===, cast(other) : self cast, clone clone, dup dup, from_json(string_or_io, root : String) : self
from_json(string_or_io) : self from_json, from_yaml(string_or_io) : self from_yaml, hash hash, inspect(io) inspect, name : String name, nilable? nilable?, to_s(io) to_s, |(other : U.class) forall U |

Class Method Detail

def self.new(block : Hash(K, V), K -> V? = nil, initial_capacity = nil) #

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def self.new(pull : YAML::PullParser, &block) #

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def self.new(initial_capacity = nil, &block : Hash(K, V), K -> V) #

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def self.new(default_value : V, initial_capacity = nil) #

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def self.new(pull : JSON::PullParser) #

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def self.new(pull : YAML::PullParser) #

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def self.zip(ary1 : Array(K), ary2 : Array(V)) #

Zips two arrays into a Hash, taking keys from ary1 and values from ary2.

Hash.zip(["key1", "key2", "key3"], ["value1", "value2", "value3"])
# => {"key1" => "value1", "key2" => "value2", "key3" => "value3"}

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Instance Method Detail

def ==(other : Hash) #

Compares with other. Returns true if all key-value pairs are the same.


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def [](key) #

See Hash#fetch


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def []=(key : K, value : V) #

Sets the value of key to the given value.

h = {} of String => String
h["foo"] = "bar"
h["foo"] # => "bar"

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def []?(key) #

Returns the value for the key given by key. If not found, returns nil. This ignores the default value set by Hash.new.

h = {"foo" => "bar"}
h["foo"]? # => "bar"
h["bar"]? # => nil

h = Hash(String, String).new("bar")
h["foo"]? # => nil

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def clear #

Empties a Hash and returns it.

hash = {"foo" => "bar"}
hash.clear # => {}

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def clone #

Similar to #dup, but duplicates the values as well.

hash_a = {"foobar" => {"foo" => "bar"}}
hash_b = hash_a.clone
hash_b["foobar"]["foo"] = "baz"
hash_a # => {"foobar" => {"foo" => "bar"}}

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def delete(key) #

Deletes the key-value pair and returns the value.

h = {"foo" => "bar"}
h.delete("foo")     # => "bar"
h.fetch("foo", nil) # => nil

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def delete_if(&block) #

Deletes each key-value pair for which the given block returns true.

h = {"foo" => "bar", "fob" => "baz", "bar" => "qux"}
h.delete_if { |key, value| key.starts_with?("fo") }
h # => { "bar" => "qux" }

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def dup #

Duplicates a Hash.

hash_a = {"foo" => "bar"}
hash_b = hash_a.dup
hash_b.merge!({"baz" => "qux"})
hash_a # => {"foo" => "bar"}

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def each #

Returns an iterator over the hash entries. Which behaves like an Iterator returning a Tuple consisting of the key and value types.

hsh = {"foo" => "bar", "baz" => "qux"}
iterator = hsh.each

iterator.next # => {"foo", "bar"}
iterator.next # => {"baz", "qux"}

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def each(&block) #

Calls the given block for each key-value pair and passes in the key and the value.

h = {"foo" => "bar"}

h.each do |key, value|
  key   # => "foo"
  value # => "bar"
end

h.each do |key_and_value|
  key_and_value # => {"foo", "bar"}
end

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def each_key #

Returns an iterator over the hash keys. Which behaves like an Iterator consisting of the key's types.

hsh = {"foo" => "bar", "baz" => "qux"}
iterator = hsh.each_key

key = iterator.next
key # => "foo"

key = iterator.next
key # => "baz"

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def each_key(&block) #

Calls the given block for each key-value pair and passes in the key.

h = {"foo" => "bar"}
h.each_key do |key|
  key # => "foo"
end

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def each_value #

Returns an iterator over the hash values. Which behaves like an Iterator consisting of the value's types.

hsh = {"foo" => "bar", "baz" => "qux"}
iterator = hsh.each_value

value = iterator.next
value # => "bar"

value = iterator.next
value # => "qux"

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def each_value(&block) #

Calls the given block for each key-value pair and passes in the value.

h = {"foo" => "bar"}
h.each_value do |value|
  value # => "bar"
end

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def empty? #

Returns true when hash contains no key-value pairs.

h = Hash(String, String).new
h.empty? # => true

h = {"foo" => "bar"}
h.empty? # => false

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def fetch(key, &block) #

Returns the value for the key given by key, or when not found calls the given block with the key.

h = {"foo" => "bar"}
h.fetch("foo") { |key| key.upcase } # => "bar"
h.fetch("bar") { |key| key.upcase } # => "BAR"

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def fetch(key) #

Returns the value for the key given by key. If not found, returns the default value given by Hash.new, otherwise raises KeyError.

h = {"foo" => "bar"}
h["foo"] # => "bar"

h = Hash(String, String).new("bar")
h["foo"] # => "bar"

h = Hash(String, String).new { "bar" }
h["foo"] # => "bar"

h = Hash(String, String).new
h["foo"] # raises KeyError

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def fetch(key, default) #

Returns the value for the key given by key, or when not found the value given by default. This ignores the default value set by Hash.new.

h = {"foo" => "bar"}
h.fetch("foo", "foo") # => "bar"
h.fetch("bar", "foo") # => "foo"

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def first_key #

Returns the first key in the hash.


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def first_key? #

Returns the first key if it exists, or returns nil.

hash = {"foo" => "bar"}
hash.first_key? # => "foo"
hash.clear
hash.first_key? # => nil

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def first_value #

Returns the first value in the hash.


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def first_value? #

Similar to #first_key?, but returns its value.


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def has_key?(key) #

Returns true when key given by key exists, otherwise false.

h = {"foo" => "bar"}
h.has_key?("foo") # => true
h.has_key?("bar") # => false

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def has_value?(val) #

Returns true when value given by value exists, otherwise false.

h = {"foo" => "bar"}
h.has_value?("foo") # => false
h.has_value?("bar") # => true

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def hash #

See Object#hash.

foo = {"foo" => "bar"}
foo.hash # => 3247054

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def inspect(io : IO) #

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def invert #

Inverts keys and values. If there are duplicated values, the last key becomes the new value.

{"foo" => "bar"}.invert                 # => {"bar" => "foo"}
{"foo" => "bar", "baz" => "bar"}.invert # => {"bar" => "baz"}

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def key(value, &block) #

Returns the first key with the given value, else yields value with the given block.

hash = {"foo" => "bar"}
hash.key("bar") { |value| value.upcase } # => "foo"
hash.key("qux") { |value| value.upcase } # => "QUX"

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def key(value) #

Returns the first key with the given value, else raises KeyError.

hash = {"foo" => "bar", "baz" => "qux"}
hash.key("bar")    # => "foo"
hash.key("qux")    # => "baz"
hash.key("foobar") # => Missing hash key for value: foobar (KeyError)

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def key?(value) #

Returns the first key with the given value, else nil.

hash = {"foo" => "bar", "baz" => "qux"}
hash.key?("bar")    # => "foo"
hash.key?("qux")    # => "baz"
hash.key?("foobar") # => nil

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def key_index(key) #

Returns the index of the given key, or nil when not found. The keys are ordered based on when they were inserted.

h = {"foo" => "bar", "baz" => "qux"}
h.key_index("foo") # => 0
h.key_index("qux") # => nil

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def keys #

Returns a new Array with all the keys.

h = {"foo" => "bar", "baz" => "bar"}
h.keys # => ["foo", "baz"]

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def merge(other : Hash(L, W)) forall L, W #

Returns a new Hash with the keys and values of this hash and other combined. A value in other takes precedence over the one in this hash.

hash = {"foo" => "bar"}
hash.merge({"baz" => "qux"})
# => {"foo" => "bar", "baz" => "qux"}
hash
# => {"foo" => "bar"}

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def merge(other : Hash(L, W), &block : K, V, W -> V | W) forall L, W #

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def merge!(other : Hash) #

Similar to #merge, but the receiver is modified.

hash = {"foo" => "bar"}
hash.merge!({"baz" => "qux"})
hash # => {"foo" => "bar", "baz" => "qux"}

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def merge!(other : Hash, &block) #

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def pretty_print(pp) : Nil #

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def rehash #

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def reject(&block : K, V -> _) #

Returns a new hash consisting of entries for which the block returns false.

h = {"a" => 100, "b" => 200, "c" => 300}
h.reject { |k, v| k > "a" } # => {"a" => 100}
h.reject { |k, v| v < 200 } # => {"b" => 200, "c" => 300}

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def reject(*keys) #

Returns a new Hash without the given keys.

{"a" => 1, "b" => 2, "c" => 3, "d" => 4}.reject("a", "c") # => {"b" => 2, "d" => 4}

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def reject!(&block : K, V -> _) #

Equivalent to Hash#reject, but makes modification on the current object rather that returning a new one. Returns nil if no changes were made.


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def reject!(keys : Array | Tuple) #

Removes a list of keys out of hash.

h = {"a" => 1, "b" => 2, "c" => 3, "d" => 4}.reject!("a", "c")
h # => {"b" => 2, "d" => 4}

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def reject!(*keys) #

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def select(&block : K, V -> _) #

Returns a new hash consisting of entries for which the block returns true.

h = {"a" => 100, "b" => 200, "c" => 300}
h.select { |k, v| k > "a" } # => {"b" => 200, "c" => 300}
h.select { |k, v| v < 200 } # => {"a" => 100}

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def select(keys : Array | Tuple) #

Returns a new Hash with the given keys.

{"a" => 1, "b" => 2, "c" => 3, "d" => 4}.select("a", "c") # => {"a" => 1, "c" => 3}

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def select(*keys) #

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def select!(&block : K, V -> _) #

Equivalent to Hash#select but makes modification on the current object rather that returning a new one. Returns nil if no changes were made


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def select!(*keys) #

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def select!(keys : Array | Tuple) #

Removes every element except the given ones.

h = {"a" => 1, "b" => 2, "c" => 3, "d" => 4}.select!("a", "c")
h # => {"a" => 1, "c" => 3}

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def shift(&block) #

Deletes and returns the first key-value pair in the hash. Yields to the given block if the hash is empty.

hash = {"foo" => "bar", "baz" => "qux"}
hash.shift { true } # => {"foo", "bar"}
hash                # => {"baz" => "qux"}

hash = {} of String => String
hash.shift { true } # => true
hash                # => {}

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def shift #

Deletes and returns the first key-value pair in the hash, or raises IndexError if the hash is empty.

hash = {"foo" => "bar", "baz" => "qux"}
hash.shift # => {"foo", "bar"}
hash       # => {"baz" => "qux"}

hash = {} of String => String
hash.shift # => Index out of bounds (IndexError)

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def shift? #

Same as #shift, but returns nil if the hash is empty.

hash = {"foo" => "bar", "baz" => "qux"}
hash.shift? # => {"foo", "bar"}
hash        # => {"baz" => "qux"}

hash = {} of String => String
hash.shift? # => nil

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def size : Int32 #

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def to_h #

Returns self.


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def to_json(io) #

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def to_s(io : IO) #

Converts to a String.

h = {"foo" => "bar"}
h.to_s       # => "{\"foo\" => \"bar\"}"
h.to_s.class # => String

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def to_yaml(emitter : YAML::Emitter) #

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def values #

Returns only the values as an Array.

h = {"foo" => "bar", "baz" => "qux"}
h.values # => ["bar", "qux"]

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def values_at(*indexes : K) #

Returns a tuple populated with the elements at the given indexes. Raises if any index is invalid.

{"a" => 1, "b" => 2, "c" => 3, "d" => 4}.values_at("a", "c") # => {1, 3}

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