Calling define_method in RubyMotion Module (v 1.27)

MTFGestures.rb

module MTFGestures
    
    def gestureRecognizerWithCompletionBlock( gestureClassString, target, completion )
        
        case gestureClassString
        
            when "UIPanGestureRecognizer" then
                
                # Define the panning delegate method based
                # on the completion handler passed to this
                # function.
                define_method "panning" do |sender|
                    completion( sender )
                end
                
                # Create the pan gesture recognizer and
                # send it along to our fake delegate method
                panGestureRecognizer = UIPanGestureRecognizer.alloc.initWithTarget( target, action:"panning" )
                self.view.addGestureRecognizer( panGestureRecognizer )
                
            else
                
                raise "#{gestureClassString} is not a supported gesture yet."
        
        end
        
    end
    
end

This module is included in another class. It's not used as a static-method Module.

An error occurs when define_method is called:

mtf_gestures.rb:12:in gestureRecognizerWithCompletionBlock:': undefined methoddefine_method' for #MTFDuoViewController:0x9d0a0b0 (NoMethodError)

MTFDuoViewController is the Class which calls "include MTFGestures"