What notifications do objects emit?

Question

I am trying to receive notifications from objects in a sketch. I can option click classes to see lists of functions and properties. Where do I find a list (besides the source) or documentation of the notifications that objects emit?

Specifically I would like to catch the TOUCHDOWN event from a button using the [self listenFor...] syntax from my C4Workspace.m

Answer 1

In general, native objects don't push notifications. For a list of C4 objects that emit them, have a look at section 2.1 and 2.2 of the following document:

http://c4ios.com/workshops/vivo/interaction.php

Buttons and other UI elements act like objects from UIKit. This means that they don't create TOUCHDOWN notifications when they are touched. They actually have a mechanism that lets them push "actions" or "messages" to other objects when various control events occur.

Instead of the following:

[self listenFor:@"TOUCHDOWN" fromObject:aButton andRunMethod:@"someMethod"];

You would do the following:

[button runMethod:@"aMethod" target:self forEvent:TOUCHDOWN];

Which allows you to bind the aMethod for the target object (here it is self) to be sent whenever the button receives a TOUCHDOWN event.

For UI elements there are a lot of different control events:

• TOUCHDOWN
• TOUCHDOWNDRAGINSIDE
• TOUCHDOWNDRAGOUTSIDE
• TOUCHDOWNDRAGENTER
• TOUCHDOWNDRAGEXIT
• TOUCHUPINSIDE
• TOUCHUPOUTSIDE
• TOUCHCANCEL
• VALUECHANGED

This is just a short list of the control events that you can use in combination with UI elements.