Easy event listener adding/removing. Put below methods in the object's .h only, and make sure the testApp has the onSomething method.

gistfile1.txt

template <class ListenerClass>
	void addEventListener(ListenerClass * listener){
        ofAddListener(onChangedEvent,listener,&ListenerClass::onSomething);        
    };
    template <class ListenerClass>
    void removeEventListener(ListenerClass * listener){
        ofRemoveListener(onChangedEvent,listener,&ListenerClass::onSomething);
    };