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require 'active_support/core_ext/object/duplicable'
require 'active_support/core_ext/array/extract_options'
# Retained for backward compatibility. Methods are now included in Class.
module ClassInheritableAttributes # :nodoc:
end
# It is recommended to use <tt>class_attribute</tt> over methods defined in this file. Please
# refer to documentation for <tt>class_attribute</tt> for more information. Officially it is not
# deprecated but <tt>class_attribute</tt> is faster.
#
# Allows attributes to be shared within an inheritance hierarchy. Each descendant gets a copy of
# their parents' attributes, instead of just a pointer to the same. This means that the child can add elements
# to, for example, an array without those additions being shared with either their parent, siblings, or
# children. This is unlike the regular class-level attributes that are shared across the entire hierarchy.
#
# The copies of inheritable parent attributes are added to subclasses when they are created, via the
# +inherited+ hook.
#
# class Person
# class_inheritable_accessor :hair_colors
# end
#
# Person.hair_colors = [:brown, :black, :blonde, :red]
# Person.hair_colors # => [:brown, :black, :blonde, :red]
# Person.new.hair_colors # => [:brown, :black, :blonde, :red]
#
# To opt out of the instance writer method, pass :instance_writer => false.
# To opt out of the instance reader method, pass :instance_reader => false.
#
# class Person
# class_inheritable_accessor :hair_colors :instance_writer => false, :instance_reader => false
# end
#
# Person.new.hair_colors = [:brown] # => NoMethodError
# Person.new.hair_colors # => NoMethodError
class Class # :nodoc:
def class_inheritable_reader(*syms)
options = syms.extract_options!
syms.each do |sym|
next if sym.is_a?(Hash)
class_eval(<<-EOS, __FILE__, __LINE__ + 1)
def self.#{sym} # def self.after_add
read_inheritable_attribute(:#{sym}) # read_inheritable_attribute(:after_add)
end # end
#
#{" #
def #{sym} # def after_add
self.class.#{sym} # self.class.after_add
end # end
" unless options[:instance_reader] == false } # # the reader above is generated unless options[:instance_reader] == false
EOS
end
end
def class_inheritable_writer(*syms)
options = syms.extract_options!
syms.each do |sym|
class_eval(<<-EOS, __FILE__, __LINE__ + 1)
def self.#{sym}=(obj) # def self.color=(obj)
write_inheritable_attribute(:#{sym}, obj) # write_inheritable_attribute(:color, obj)
end # end
#
#{" #
def #{sym}=(obj) # def color=(obj)
self.class.#{sym} = obj # self.class.color = obj
end # end
" unless options[:instance_writer] == false } # # the writer above is generated unless options[:instance_writer] == false
EOS
end
end
def class_inheritable_array_writer(*syms)
options = syms.extract_options!
syms.each do |sym|
class_eval(<<-EOS, __FILE__, __LINE__ + 1)
def self.#{sym}=(obj) # def self.levels=(obj)
write_inheritable_array(:#{sym}, obj) # write_inheritable_array(:levels, obj)
end # end
#
#{" #
def #{sym}=(obj) # def levels=(obj)
self.class.#{sym} = obj # self.class.levels = obj
end # end
" unless options[:instance_writer] == false } # # the writer above is generated unless options[:instance_writer] == false
EOS
end
end
def class_inheritable_hash_writer(*syms)
options = syms.extract_options!
syms.each do |sym|
class_eval(<<-EOS, __FILE__, __LINE__ + 1)
def self.#{sym}=(obj) # def self.nicknames=(obj)
write_inheritable_hash(:#{sym}, obj) # write_inheritable_hash(:nicknames, obj)
end # end
#
#{" #
def #{sym}=(obj) # def nicknames=(obj)
self.class.#{sym} = obj # self.class.nicknames = obj
end # end
" unless options[:instance_writer] == false } # # the writer above is generated unless options[:instance_writer] == false
EOS
end
end
def class_inheritable_accessor(*syms)
class_inheritable_reader(*syms)
class_inheritable_writer(*syms)
end
def class_inheritable_array(*syms)
class_inheritable_reader(*syms)
class_inheritable_array_writer(*syms)
end
def class_inheritable_hash(*syms)
class_inheritable_reader(*syms)
class_inheritable_hash_writer(*syms)
end
def inheritable_attributes
@inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
end
def write_inheritable_attribute(key, value)
if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
@inheritable_attributes = {}
end
inheritable_attributes[key] = value
end
def write_inheritable_array(key, elements)
write_inheritable_attribute(key, []) if read_inheritable_attribute(key).nil?
write_inheritable_attribute(key, read_inheritable_attribute(key) + elements)
end
def write_inheritable_hash(key, hash)
write_inheritable_attribute(key, {}) if read_inheritable_attribute(key).nil?
write_inheritable_attribute(key, read_inheritable_attribute(key).merge(hash))
end
def read_inheritable_attribute(key)
inheritable_attributes[key]
end
def reset_inheritable_attributes
@inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
end
private
# Prevent this constant from being created multiple times
EMPTY_INHERITABLE_ATTRIBUTES = {}.freeze
def inherited_with_inheritable_attributes(child)
inherited_without_inheritable_attributes(child) if respond_to?(:inherited_without_inheritable_attributes)
if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
new_inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
else
new_inheritable_attributes = Hash[inheritable_attributes.map do |(key, value)|
[key, value.duplicable? ? value.dup : value]
end]
end
child.instance_variable_set('@inheritable_attributes', new_inheritable_attributes)
end
alias inherited_without_inheritable_attributes inherited
alias inherited inherited_with_inheritable_attributes
end
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