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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.

Methods
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Class Public methods
[](*args)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 81
def self.[](*args)
  new.merge!(Hash[*args])
end
new(constructor = {})
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 57
def initialize(constructor = {})
  if constructor.respond_to?(:to_hash)
    super()
    update(constructor.to_hash)
  else
    super(constructor)
  end
end
new_from_hash_copying_default(hash)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 74
def self.new_from_hash_copying_default(hash)
  hash = hash.to_hash
  new(hash).tap do |new_hash|
    new_hash.default = hash.default
  end
end
Instance Public methods
[]=(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 94
def []=(key, value)
  regular_writer(convert_key(key), convert_value(value, for: :assignment))
end
deep_stringify_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 224
def deep_stringify_keys; dup end
deep_stringify_keys!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 222
def deep_stringify_keys!; self end
deep_symbolize_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 228
def deep_symbolize_keys; to_hash.deep_symbolize_keys! end
default(key = nil)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 66
def default(key = nil)
  if key.is_a?(Symbol) && include?(key = key.to_s)
    self[key]
  else
    super
  end
end
delete(key)

Removes the specified key from the hash.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 217
def delete(key)
  super(convert_key(key))
end
dup()

Returns an exact copy of the hash.

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 180
def dup
  self.class.new(self).tap do |new_hash|
    new_hash.default = default
  end
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 45
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 165
def fetch(key, *extras)
  super(convert_key(key), *extras)
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 147
def key?(key)
  super(convert_key(key))
end
member?(key)
Alias for: key?
merge(hash, &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 189
def merge(hash, &block)
  self.dup.update(hash, &block)
end
merge!(other_hash)
Alias for: update
nested_under_indifferent_access()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 53
def nested_under_indifferent_access
  self
end
regular_update(other_hash)
Alias for: update
regular_writer(key, value)
Alias for: []=
reject(*args, &block)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 235
def reject(*args, &block)
  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 212
def replace(other_hash)
  super(self.class.new_from_hash_copying_default(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}
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 199
def reverse_merge(other_hash)
  super(self.class.new_from_hash_copying_default(other_hash))
end
reverse_merge!(other_hash)

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

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 204
def reverse_merge!(other_hash)
  replace(reverse_merge( other_hash ))
end
select(*args, &block)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 231
def select(*args, &block)
  dup.tap { |hash| hash.select!(*args, &block) }
end
store(key, value)
Alias for: []=
stringify_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 223
def stringify_keys; dup end
stringify_keys!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 221
def stringify_keys!; self end
symbolize_keys()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 227
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 240
def to_hash
  _new_hash= {}
  each do |key, value|
    _new_hash[convert_key(key)] = convert_value(value, for: :to_hash)
  end
  Hash.new(default).merge!(_new_hash)
end
to_options!()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 229
def to_options!; self end
update(other_hash)

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}
Also aliased as: regular_update, merge!
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 125
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
values_at(*indices)

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 175
def values_at(*indices)
  indices.collect { |key| self[convert_key(key)] }
end
with_indifferent_access()
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 49
def with_indifferent_access
  dup
end
Instance Protected methods
convert_key(key)
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 249
def convert_key(key)
  key.kind_of?(Symbol) ? key.to_s : key
end
convert_value(value, options = {})
# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 253
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)
    unless options[:for] == :assignment
      value = value.dup
    end
    value.map! { |e| convert_value(e, options) }
  else
    value
  end
end