class Object::HashWithIndifferentAccess

Parent:: Hash

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.

Public Class Methods

[](*args) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 83
def self.[](*args)
  new.merge!(Hash[*args])
end

new(constructor = {}) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 58
def initialize(constructor = {})
  if constructor.respond_to?(:to_hash)
    super()
    update(constructor)
  else
    super(constructor)
  end
end

Calls superclass method

new_from_hash_copying_default(hash) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 75
def self.new_from_hash_copying_default(hash)
  hash = hash.to_hash
  new(hash).tap do |new_hash|
    new_hash.default = hash.default
    new_hash.default_proc = hash.default_proc if hash.default_proc
  end
end

Public Instance Methods

[]=(key, value) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 96
def []=(key, value)
  regular_writer(convert_key(key), convert_value(value, for: :assignment))
end

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

compact() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 253
def compact
  dup.tap(&:compact!)
end

deep_stringify_keys() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 233
def deep_stringify_keys; dup end

deep_stringify_keys!() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 231
def deep_stringify_keys!; self end

deep_symbolize_keys() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 237
def deep_symbolize_keys; to_hash.deep_symbolize_keys! end

default(key = nil) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 67
def default(key = nil)
  if key.is_a?(Symbol) && include?(key = key.to_s)
    self[key]
  else
    super
  end
end

Calls superclass method

delete(key) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 226
def delete(key)
  super(convert_key(key))
end

Removes the specified key from the hash.

Calls superclass method

dup() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 189
def dup
  self.class.new(self).tap do |new_hash|
    set_defaults(new_hash)
  end
end

Returns a shallow copy of the hash.

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

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

extractable_options?() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 46
def extractable_options?
  true
end

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

fetch(key, *extras) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 167
def fetch(key, *extras)
  super(convert_key(key), *extras)
end

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

has_key?(key)

Alias for: key?

include?(key)

Alias for: key?

key?(key) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 149
def key?(key)
  super(convert_key(key))
end

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

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

member?(key)

Alias for: key?

merge(hash, &block) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 198
def merge(hash, &block)
  self.dup.update(hash, &block)
end

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.

merge!(other_hash)

Alias for: update

nested_under_indifferent_access() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 54
def nested_under_indifferent_access
  self
end

regular_update(other_hash)

Alias for: update

regular_writer(key, value)

Alias for: []=

reject(*args, &block) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 244
def reject(*args, &block)
  dup.tap { |hash| hash.reject!(*args, &block) }
end

replace(other_hash) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 221
def replace(other_hash)
  super(self.class.new_from_hash_copying_default(other_hash))
end

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

reverse_merge(other_hash) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 208
def reverse_merge(other_hash)
  super(self.class.new_from_hash_copying_default(other_hash))
end

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

reverse_merge!(other_hash) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 213
def reverse_merge!(other_hash)
  replace(reverse_merge( other_hash ))
end

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

select(*args, &block) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 240
def select(*args, &block)
  dup.tap { |hash| hash.select!(*args, &block) }
end

store(key, value)

Alias for: []=

stringify_keys() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 232
def stringify_keys; dup end

stringify_keys!() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 230
def stringify_keys!; self end

symbolize_keys() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 236
def symbolize_keys; to_hash.symbolize_keys! end

to_hash() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 258
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

Convert to a regular hash with string keys.

to_options!() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 238
def to_options!; self end

transform_values(*args, &block) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 248
def transform_values(*args, &block)
  return to_enum(:transform_values) unless block_given?
  dup.tap { |hash| hash.transform_values!(*args, &block) }
end

update(other_hash) { |convert_key(key), self, value| ... } Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 127
def update(other_hash)
  if other_hash.is_a? HashWithIndifferentAccess
    super(other_hash)
  else
    other_hash.to_hash.each_pair do |key, value|
      if block_given? && key?(key)
        value = yield(convert_key(key), self[key], value)
      end
      regular_writer(convert_key(key), convert_value(value))
    end
    self
  end
end

Updates the receiver in-place, merging in the hash passed as argument:

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!"}

The argument 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}

Calls superclass method

Also aliased as: regular_update, merge!

values_at(*indices) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 177
def values_at(*indices)
  indices.collect { |key| self[convert_key(key)] }
end

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"]

with_indifferent_access() Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 50
def with_indifferent_access
  dup
end

Protected Instance Methods

convert_key(key) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 269
def convert_key(key)
  key.kind_of?(Symbol) ? key.to_s : key
end

convert_value(value, options = {}) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 273
def convert_value(value, options = {})
  if value.is_a? Hash
    if options[:for] == :to_hash
      value.to_hash
    else
      value.nested_under_indifferent_access
    end
  elsif value.is_a?(Array)
    if options[:for] != :assignment || value.frozen?
      value = value.dup
    end
    value.map! { |e| convert_value(e, options) }
  else
    value
  end
end

set_defaults(target) Show source

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 290
def set_defaults(target)
  if default_proc
    target.default_proc = default_proc.dup
  else
    target.default = default
  end
end