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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.

Methods
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Class Public methods
[](*args)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 80
def self.[](*args)
  new.merge!(Hash[*args])
end
new(constructor = {})
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 67
def initialize(constructor = {})
  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
  else
    super(constructor)
  end
end
Instance Public 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
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 163
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'.

Also aliased as: regular_writer, store
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 93
def []=(key, value)
  regular_writer(convert_key(key), convert_value(value, for: :assignment))
end
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
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 176
def assoc(key)
  super(convert_key(key))
end
compact()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 350
def compact
  dup.tap(&:compact!)
end
deep_stringify_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 304
def deep_stringify_keys; dup end
deep_stringify_keys!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 302
def deep_stringify_keys!; self end
deep_symbolize_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 309
def deep_symbolize_keys; to_hash.deep_symbolize_keys! end
default(*args)

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'
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 218
def default(*args)
  super(*args.map { |arg| convert_key(arg) })
end
delete(key)

Removes the specified key from the hash.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 292
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
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 203
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 253
def dup
  self.class.new(self).tap do |new_hash|
    set_defaults(new_hash)
  end
end
except(*keys)
Also aliased as: without
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 296
def except(*keys)
  slice(*self.keys - keys.map { |key| convert_key(key) })
end
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 55
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"
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 190
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"
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 241
def fetch_values(*indices, &block)
  super(*indices.map { |key| convert_key(key) }, &block)
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
Also aliased as: include?, has_key?, member?
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 146
def key?(key)
  super(convert_key(key))
end
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 262
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 63
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 317
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}
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 287
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}
Also aliased as: with_defaults
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 272
def reverse_merge(other_hash)
  super(self.class.new(other_hash))
end
reverse_merge!(other_hash)

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

Also aliased as: with_defaults!
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 278
def reverse_merge!(other_hash)
  super(self.class.new(other_hash))
end
select(*args, &block)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 312
def select(*args, &block)
  return to_enum(:select) unless block_given?
  dup.tap { |hash| hash.select!(*args, &block) }
end
slice(*keys)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 340
def slice(*keys)
  keys.map! { |key| convert_key(key) }
  self.class.new(super)
end
slice!(*keys)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 345
def slice!(*keys)
  keys.map! { |key| convert_key(key) }
  super
end
store(key, value)
Alias for: []=
stringify_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 303
def stringify_keys; dup end
stringify_keys!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 301
def stringify_keys!; self end
symbolize_keys()
Also aliased as: to_options
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 307
def symbolize_keys; to_hash.symbolize_keys! end
to_hash()

Convert to a regular hash with string keys.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 355
def to_hash
  _new_hash = Hash.new
  set_defaults(_new_hash)

  each do |key, value|
    _new_hash[key] = convert_value(value, for: :to_hash)
  end
  _new_hash
end
to_options()
Alias for: symbolize_keys
to_options!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 310
def to_options!; self end
transform_keys(*args, &block)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 327
def transform_keys(*args, &block)
  return to_enum(:transform_keys) unless block_given?
  dup.tap { |hash| hash.transform_keys!(*args, &block) }
end
transform_keys!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 332
def transform_keys!
  return enum_for(:transform_keys!) { size } unless block_given?
  keys.each do |key|
    self[yield(key)] = delete(key)
  end
  self
end
transform_values(*args, &block)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 322
def transform_values(*args, &block)
  return to_enum(:transform_values) unless block_given?
  dup.tap { |hash| hash.transform_values!(*args, &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}
Also aliased as: regular_update, merge!
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 127
def update(*other_hashes, &block)
  if other_hashes.one?
    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
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"]
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 228
def values_at(*keys)
  super(*keys.map { |key| convert_key(key) })
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 59
def with_indifferent_access
  dup
end
without(*keys)
Alias for: except
Instance Private methods
convert_key(key)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 366
def convert_key(key) # :doc:
  key.kind_of?(Symbol) ? key.to_s : key
end
convert_value(value, for: nil)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 370
def convert_value(value, for: nil) # :doc:
  conversion = binding.local_variable_get(:for)

  if value.is_a? Hash
    if conversion == :to_hash
      value.to_hash
    else
      value.nested_under_indifferent_access
    end
  elsif value.is_a?(Array)
    if conversion != :assignment || value.frozen?
      value = value.dup
    end
    value.map! { |e| convert_value(e, for: conversion) }
  else
    value
  end
end
set_defaults(target)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 389
def set_defaults(target) # :doc:
  if default_proc
    target.default_proc = default_proc.dup
  else
    target.default = default
  end
end