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# frozen-string-literal: true
module Sequel
module Plugins
# The subclasses plugin keeps track of all subclasses of the
# current model class. Direct subclasses are available via the
# subclasses method, and all descendent classes are available via the
# descendents method:
#
# c = Class.new(Sequel::Model)
# c.plugin :subclasses
# sc1 = Class.new(c)
# sc2 = Class.new(c)
# ssc1 = Class.new(sc1)
# c.subclasses # [sc1, sc2]
# sc1.subclasses # [ssc1]
# sc2.subclasses # []
# ssc1.subclasses # []
# c.descendents # [sc1, ssc1, sc2]
#
# You can also finalize the associations and then freeze the classes
# in all descendent classes. Doing so is a recommended practice after
# all models have been defined in production and testing, and this makes
# it easier than keeping track of the classes to finalize and freeze
# manually:
#
# c.freeze_descendants
#
# You can provide a block when loading the plugin, and it will be called
# with each subclass created:
#
# a = []
# Sequel::Model.plugin(:subclasses){|sc| a << sc}
# class A < Sequel::Model; end
# class B < Sequel::Model; end
# a # => [A, B]
module Subclasses
# Initialize the subclasses instance variable for the model.
def self.apply(model, &block)
model.instance_variable_set(:@subclasses, [])
model.instance_variable_set(:@on_subclass, block)
end
module ClassMethods
# Callable object that should be called with every descendent
# class created.
attr_reader :on_subclass
# All subclasses for the current model. Does not
# include the model itself.
attr_reader :subclasses
# All descendent classes of this model.
def descendents
Sequel.synchronize{subclasses.dup}.map{|x| [x] + x.send(:descendents)}.flatten
end
# Freeze all descendent classes. This also finalizes the associations for those
# classes before freezing.
def freeze_descendents
descendents.each(&:finalize_associations).each(&:freeze)
end
Plugins.inherited_instance_variables(self, :@subclasses=>lambda{|v| []}, :@on_subclass=>nil)
private
# Add the subclass to this model's current subclasses,
# and initialize a new subclasses instance variable
# in the subclass.
def inherited(subclass)
super
Sequel.synchronize{subclasses << subclass}
on_subclass.call(subclass) if on_subclass
end
end
end
end
end
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