dm-core activate callbacks example.rb

        def destroy
          sads = self_and_descendents
          hooks = self.class.const_get('INSTANCE_HOOKS')
          before_methods = hooks[:destroy][:before].map { |hash| hash[:name] }
          after_methods =  hooks[:destroy][:after].map  { |hash| hash[:name] }
          # Trigger all the before :destroy methods
          sads.each { |sad| before_methods.each { |bf| sad.send(bf) } }
          # dup is called here because destroy! likes to clear out the array, understandably.
          sads.dup.destroy!
          # Now go through after all the after :destroy methods.
          sads.each { |sad| after_methods.each { |bf| sad.send(bf) } }
        end