Module: SubclassAware

Defined in:
lib/classy/subclass_aware.rb

Overview

SubclassAware allows a class to know about all of the subclasses that descend from it in the inheritance tree.

Example

class Parent
  extend SubclassAware
end

class ChildA < Parent
end

class ChildB < Parent
end

Class ChildB1 < ChildB
end

Parent.subclasses   # => [ ChildA, ChildB, ChildB1 ]

Note

SubclassAware sets and maintains the class variable @@classy_subclasses on the extending class, so in the unlikely event that this class variable is already in use, unusual bugs may result.

Warning

This module defines an inherited() class method. If the extending class defines its own inherited() method without calling super, this inherited() method is lost and subclass tracking will break. In order to work around this, make sure your inherited() method calls super. Like this:

class YourAwesomeClass

def self.inherited
  # ...your awesome logic
  super  # <-- This is important.
end

end

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.extended(klass) ⇒ Object

Instantiate a new Set of subclasses. Not intended to be called directly.



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# File 'lib/classy/subclass_aware.rb', line 49

def self.extended(klass)
  klass.class_exec { class_variable_set(:@@classy_subclasses, Set.new) }
end

Instance Method Details

#forget_subclasses ⇒ Object

Clear all info about known subclasses. This method is probably mainly useful for testing.



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# File 'lib/classy/subclass_aware.rb', line 71

def forget_subclasses
  class_exec { class_variable_get(:@@classy_subclasses).clear }
end

#inherited(sub) ⇒ Object

Add the inheriting class to the list of subclasses. Not intended to be called directly.



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# File 'lib/classy/subclass_aware.rb', line 56

def inherited(sub)
  class_exec { class_variable_get(:@@classy_subclasses).add sub }
  super
end

#subclasses ⇒ Object

Return an array of all known subclasses (and sub-subclasses, etc) of this class.



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# File 'lib/classy/subclass_aware.rb', line 64

def subclasses
  class_exec { class_variable_get(:@@classy_subclasses).to_a }
end