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 = inheritable_attributes.inject({}) do |memo, (key, value)|
memo.update(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
class Class
# Defines class-level inheritable attribute reader. Attributes are available to subclasses,
# each subclass has a copy of parent's attribute.
#
# @param *syms<Array[#to_s]> Array of attributes to define inheritable reader for.
# @return <Array[#to_s]> Array of attributes converted into inheritable_readers.
#
# @api public
#
# @todo Do we want to block instance_reader via :instance_reader => false
# @todo It would be preferable that we do something with a Hash passed in
# (error out or do the same as other methods above) instead of silently
# moving on). In particular, this makes the return value of this function
# less useful.
def extlib_inheritable_reader(*ivars, &block)
options = ivars.extract_options!
ivars.each do |ivar|
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def self.#{ivar}
return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
ivar = superclass.#{ivar}
return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
@#{ivar} = ivar.duplicable? ? ivar.dup : ivar
end
RUBY
unless options[:instance_reader] == false
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def #{ivar}
self.class.#{ivar}
end
RUBY
end
instance_variable_set(:"@#{ivar}", yield) if block_given?
end
end
# Defines class-level inheritable attribute writer. Attributes are available to subclasses,
# each subclass has a copy of parent's attribute.
#
# @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
# define inheritable writer for.
# @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
# @return <Array[#to_s]> An Array of the attributes that were made into inheritable writers.
#
# @api public
#
# @todo We need a style for class_eval <<-HEREDOC. I'd like to make it
# class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.
def extlib_inheritable_writer(*ivars)
options = ivars.extract_options!
ivars.each do |ivar|
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def self.#{ivar}=(obj)
@#{ivar} = obj
end
RUBY
unless options[:instance_writer] == false
self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
def #{ivar}=(obj) self.class.#{ivar} = obj end
RUBY
end
self.send("#{ivar}=", yield) if block_given?
end
end
# Defines class-level inheritable attribute accessor. Attributes are available to subclasses,
# each subclass has a copy of parent's attribute.
#
# @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
# define inheritable accessor for.
# @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
# @return <Array[#to_s]> An Array of attributes turned into inheritable accessors.
#
# @api public
def extlib_inheritable_accessor(*syms, &block)
extlib_inheritable_reader(*syms)
extlib_inheritable_writer(*syms, &block)
end
end
