class ActiveSupport::HashWithIndifferentAccess

Hash With Indifferent Access¶ ↑

Implements a hash where keys :foo and "foo" are considered to be the same.

rgb = ActiveSupport::HashWithIndifferentAccess.new

rgb[:black] = '#000000'
rgb[:black]  # => '#000000'
rgb['black'] # => '#000000'

rgb['white'] = '#FFFFFF'
rgb[:white]  # => '#FFFFFF'
rgb['white'] # => '#FFFFFF'

Internally symbols are mapped to strings when used as keys in the entire writing interface (calling []=, merge, etc). This mapping belongs to the public interface. For example, given:

hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1)

You are guaranteed that the key is returned as a string:

hash.keys # => ["a"]

Technically other types of keys are accepted:

hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1)
hash[0] = 0
hash # => {"a"=>1, 0=>0}

but this class is intended for use cases where strings or symbols are the expected keys and it is convenient to understand both as the same. For example the params hash in Ruby on Rails.

Note that core extensions define Hash#with_indifferent_access:

rgb = { black: '#000000', white: '#FFFFFF' }.with_indifferent_access

which may be handy.

To access this class outside of Rails, require the core extension with:

require "active_support/core_ext/hash/indifferent_access"

which will, in turn, require this file.

Public Class Methods

[] (*args)

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 85
def self.[](*args)
  new.merge!(Hash[*args])
end

new (constructor = nil)

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 70
def initialize(constructor = nil)
  if constructor.respond_to?(:to_hash)
    super()
    update(constructor)

    hash = constructor.is_a?(Hash) ? constructor : constructor.to_hash
    self.default = hash.default if hash.default
    self.default_proc = hash.default_proc if hash.default_proc
  elsif constructor.nil?
    super()
  else
    super(constructor)
  end
end

Public Instance Methods

[] (key)

Same as Hash#[] where the key passed as argument can be either a string or a symbol:

counters = ActiveSupport::HashWithIndifferentAccess.new
counters[:foo] = 1

counters['foo'] # => 1
counters[:foo]  # => 1
counters[:zoo]  # => nil

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 168
def [](key)
  super(convert_key(key))
end

[]= (key, value)

Assigns a new value to the hash:

hash = ActiveSupport::HashWithIndifferentAccess.new
hash[:key] = 'value'

This value can be later fetched using either :key or 'key'.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 98
def []=(key, value)
  regular_writer(convert_key(key), convert_value(value, conversion: :assignment))
end

Also aliased as: regular_writer, store

assoc (key)

Same as Hash#assoc where the key passed as argument can be either a string or a symbol:

counters = ActiveSupport::HashWithIndifferentAccess.new
counters[:foo] = 1

counters.assoc('foo') # => ["foo", 1]
counters.assoc(:foo)  # => ["foo", 1]
counters.assoc(:zoo)  # => nil

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 181
def assoc(key)
  super(convert_key(key))
end

compact ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 371
def compact
  dup.tap(&:compact!)
end

deep_symbolize_keys ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 320
def deep_symbolize_keys; to_hash.deep_symbolize_keys! end

default (key = (no_key = true))

Same as Hash#default where the key passed as argument can be either a string or a symbol:

hash = ActiveSupport::HashWithIndifferentAccess.new(1)
hash.default                   # => 1

hash = ActiveSupport::HashWithIndifferentAccess.new { |hash, key| key }
hash.default                   # => nil
hash.default('foo')            # => 'foo'
hash.default(:foo)             # => 'foo'

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 223
def default(key = (no_key = true))
  if no_key
    super()
  else
    super(convert_key(key))
  end
end

delete (key)

Removes the specified key from the hash.

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 303
def delete(key)
  super(convert_key(key))
end

dig (*args)

Same as Hash#dig where the key passed as argument can be either a string or a symbol:

counters = ActiveSupport::HashWithIndifferentAccess.new
counters[:foo] = { bar: 1 }

counters.dig('foo', 'bar')     # => 1
counters.dig(:foo, :bar)       # => 1
counters.dig(:zoo)             # => nil

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 208
def dig(*args)
  args[0] = convert_key(args[0]) if args.size > 0
  super(*args)
end

dup ()

Returns a shallow copy of the hash.

hash = ActiveSupport::HashWithIndifferentAccess.new({ a: { b: 'b' } })
dup  = hash.dup
dup[:a][:c] = 'c'

hash[:a][:c] # => "c"
dup[:a][:c]  # => "c"

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 264
def dup
  self.class.new(self).tap do |new_hash|
    set_defaults(new_hash)
  end
end

except (*keys)

Returns a hash with indifferent access that includes everything except given keys.

hash = { a: "x", b: "y", c: 10 }.with_indifferent_access
hash.except(:a, "b") # => {c: 10}.with_indifferent_access
hash                 # => { a: "x", b: "y", c: 10 }.with_indifferent_access

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 311
def except(*keys)
  dup.except!(*keys)
end

Also aliased as: without

extractable_options? ()

Returns true so that Array#extract_options! finds members of this class.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 58
def extractable_options?
  true
end

fetch (key, *extras)

Same as Hash#fetch where the key passed as argument can be either a string or a symbol:

counters = ActiveSupport::HashWithIndifferentAccess.new
counters[:foo] = 1

counters.fetch('foo')          # => 1
counters.fetch(:bar, 0)        # => 0
counters.fetch(:bar) { |key| 0 } # => 0
counters.fetch(:zoo)           # => KeyError: key not found: "zoo"

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 195
def fetch(key, *extras)
  super(convert_key(key), *extras)
end

fetch_values (*indices, &block)

Returns an array of the values at the specified indices, but also raises an exception when one of the keys can’t be found.

hash = ActiveSupport::HashWithIndifferentAccess.new
hash[:a] = 'x'
hash[:b] = 'y'
hash.fetch_values('a', 'b') # => ["x", "y"]
hash.fetch_values('a', 'c') { |key| 'z' } # => ["x", "z"]
hash.fetch_values('a', 'c') # => KeyError: key not found: "c"

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 251
def fetch_values(*indices, &block)
  indices.map! { |key| convert_key(key) }
  super
end

has_key? (key)

Alias for: key?

include? (key)

Alias for: key?

key? (key)

Checks the hash for a key matching the argument passed in:

hash = ActiveSupport::HashWithIndifferentAccess.new
hash['key'] = 'value'
hash.key?(:key)  # => true
hash.key?('key') # => true

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 151
def key?(key)
  super(convert_key(key))
end

Also aliased as: include?, has_key?, member?

member? (key)

Alias for: key?

merge (*hashes, &block)

This method has the same semantics of update, except it does not modify the receiver but rather returns a new hash with indifferent access with the result of the merge.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 273
def merge(*hashes, &block)
  dup.update(*hashes, &block)
end

merge! (*other_hashes, &block)

Alias for: update

nested_under_indifferent_access ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 66
def nested_under_indifferent_access
  self
end

regular_update (*other_hashes, &block)

Alias for: update

regular_writer (key, value)

Alias for: []=

reject (*args, &block)

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 328
def reject(*args, &block)
  return to_enum(:reject) unless block_given?
  dup.tap { |hash| hash.reject!(*args, &block) }
end

replace (other_hash)

Replaces the contents of this hash with other_hash.

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

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 298
def replace(other_hash)
  super(self.class.new(other_hash))
end

reverse_merge (other_hash)

Like merge but the other way around: Merges the receiver into the argument and returns a new hash with indifferent access as result:

hash = ActiveSupport::HashWithIndifferentAccess.new
hash['a'] = nil
hash.reverse_merge(a: 0, b: 1) # => {"a"=>nil, "b"=>1}

Calls superclass method Hash#reverse_merge

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 283
def reverse_merge(other_hash)
  super(self.class.new(other_hash))
end

Also aliased as: with_defaults

reverse_merge! (other_hash)

Same semantics as reverse_merge but modifies the receiver in-place.

Calls superclass method Hash#reverse_merge!

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 289
def reverse_merge!(other_hash)
  super(self.class.new(other_hash))
end

Also aliased as: with_defaults!

select (*args, &block)

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 323
def select(*args, &block)
  return to_enum(:select) unless block_given?
  dup.tap { |hash| hash.select!(*args, &block) }
end

slice (*keys)

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 361
def slice(*keys)
  keys.map! { |key| convert_key(key) }
  self.class.new(super)
end

slice! (*keys)

Calls superclass method Hash#slice!

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 366
def slice!(*keys)
  keys.map! { |key| convert_key(key) }
  super
end

store (key, value)

Alias for: []=

symbolize_keys ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 318
def symbolize_keys; to_hash.symbolize_keys! end

Also aliased as: to_options

to_hash ()

Convert to a regular hash with string keys.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 376
def to_hash
  copy = Hash[self]
  copy.transform_values! { |v| convert_value_to_hash(v) }
  set_defaults(copy)
  copy
end

to_options ()

Alias for: symbolize_keys

to_options! ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 321
def to_options!; self end

to_proc ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 383
def to_proc
  proc { |key| self[key] }
end

transform_keys (hash = NOT_GIVEN, &block)

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 340
def transform_keys(hash = NOT_GIVEN, &block)
  return to_enum(:transform_keys) if NOT_GIVEN.equal?(hash) && !block_given?
  dup.tap { |h| h.transform_keys!(hash, &block) }
end

transform_keys! (hash = NOT_GIVEN) { |key| ... }

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 345
def transform_keys!(hash = NOT_GIVEN, &block)
  return to_enum(:transform_keys!) if NOT_GIVEN.equal?(hash) && !block_given?

  if hash.nil?
    super
  elsif NOT_GIVEN.equal?(hash)
    keys.each { |key| self[yield(key)] = delete(key) }
  elsif block_given?
    keys.each { |key| self[hash[key] || yield(key)] = delete(key) }
  else
    keys.each { |key| self[hash[key] || key] = delete(key) }
  end

  self
end

transform_values (&block)

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 333
def transform_values(&block)
  return to_enum(:transform_values) unless block_given?
  dup.tap { |hash| hash.transform_values!(&block) }
end

update (*other_hashes, &block)

Updates the receiver in-place, merging in the hashes passed as arguments:

hash_1 = ActiveSupport::HashWithIndifferentAccess.new
hash_1[:key] = 'value'

hash_2 = ActiveSupport::HashWithIndifferentAccess.new
hash_2[:key] = 'New Value!'

hash_1.update(hash_2) # => {"key"=>"New Value!"}

hash = ActiveSupport::HashWithIndifferentAccess.new
hash.update({ "a" => 1 }, { "b" => 2 }) # => { "a" => 1, "b" => 2 }

The arguments can be either an ActiveSupport::HashWithIndifferentAccess or a regular Hash. In either case the merge respects the semantics of indifferent access.

If the argument is a regular hash with keys :key and "key" only one of the values end up in the receiver, but which one is unspecified.

When given a block, the value for duplicated keys will be determined by the result of invoking the block with the duplicated key, the value in the receiver, and the value in other_hash. The rules for duplicated keys follow the semantics of indifferent access:

hash_1[:key] = 10
hash_2['key'] = 12
hash_1.update(hash_2) { |key, old, new| old + new } # => {"key"=>22}

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 132
def update(*other_hashes, &block)
  if other_hashes.size == 1
    update_with_single_argument(other_hashes.first, block)
  else
    other_hashes.each do |other_hash|
      update_with_single_argument(other_hash, block)
    end
  end
  self
end

Also aliased as: regular_update, merge!

values_at (*keys)

Returns an array of the values at the specified indices:

hash = ActiveSupport::HashWithIndifferentAccess.new
hash[:a] = 'x'
hash[:b] = 'y'
hash.values_at('a', 'b') # => ["x", "y"]

Calls superclass method

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 237
def values_at(*keys)
  keys.map! { |key| convert_key(key) }
  super
end

with_defaults (other_hash)

Alias for: reverse_merge

with_defaults! (other_hash)

Alias for: reverse_merge!

with_indifferent_access ()

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 62
def with_indifferent_access
  dup
end

without (*keys)

Alias for: except