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# encoding: utf-8
require 'thread_safe'
# Module that adds descendant tracking to a class
module DescendantsTracker
# Return the descendants of this class
#
# @example
# descendants = ParentClass.descendants
#
# @return [Array<Class<DescendantsTracker>>]
#
# @api public
attr_reader :descendants
# Setup the class for descendant tracking
#
# @param [Class<DescendantsTracker>] descendant
#
# @return [undefined]
#
# @api private
def self.setup(descendant)
descendant.instance_variable_set(:@descendants, ThreadSafe::Array.new)
end
class << self
alias_method :extended, :setup
private :extended
end
# Add the descendant to this class and the superclass
#
# @param [Class] descendant
#
# @return [self]
#
# @api private
def add_descendant(descendant)
ancestor = superclass
if ancestor.respond_to?(:add_descendant)
ancestor.add_descendant(descendant)
end
descendants.unshift(descendant)
self
end
private
# Hook called when class is inherited
#
# @param [Class] descendant
#
# @return [self]
#
# @api private
def inherited(descendant)
super
DescendantsTracker.setup(descendant)
add_descendant(descendant)
end
end # module DescendantsTracker
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