July 10th, 2007
Getting a class' subclasses
I needed a way to get a list of the subclasses that inherit a specific. Unfortunately there is no method like Class.subclasses (there is Class.superclass, though) so I had to look for another way to achieve this. Let’s say, we want to have an array containing all subclasses as a class variable of our superclass Strategy. In order to fill the array we’ll overwrite the inherited class method of Class. (Already confused by all the classes? ;-))
1 class Strategy 2 @@subclasses = Array.new 3 class << self 4 def inherited(klass) 5 @@subclasses << klass 6 end 7 8 def subclasses 9 @@subclasses.join(', ') 10 end 11 end 12 end
Now, every time a class extends Strategy our new inherited method is called and adds the class to our array.
1 class StrategyA < Strategy; end 2 class StrategyB < Strategy; end 3 class StrategyC < Strategy; end 4 5 # Let's get the current list of subclasses 6 puts Strategy.subclasses # will output StrategyA, StrategyB, StrategyC
What happens if a class inherits any of our subclasses? Well, as long as you don’t overwrite the inherited method again it’s also added to the array.
