testApp.cpp

#include "testApp.h"

void testApp::setup()
{
    updateHandler = drawHandler = &testApp::empty;
}

void testApp::update()
{
    (this->*updateHandler)();
}

void testApp::draw()
{
    (this->*drawHandler)();
}

void testApp::mousePressed(int x, int y, int button)
{
    updateHandler = &testApp::updateSomething;
    drawHandler = &testApp::drawSomething;
}

void testApp::mouseReleased(int x, int y, int button)
{
    updateHandler = drawHandler = &testApp::empty;
}

void testApp::updateSomething()
{
    // (snip)
}

void testApp::drawSomething()
{
    // (snip)
}

void testApp::empty()
{
    // do nothing.
}

testApp.h

#include "ofMain.h"

class testApp:public ofBaseApp
{
    // (snip)
    private:
        void updateSomething();
        void drawSomething();
        void empty();

        void (testApp::*updateHandler)();
        void (testApp::*drawHandler)();
}