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c4

What notifications do objects emit?

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

Solution

  • 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.