iPhone Obj-C Properties

Question

Hi, I'm a beginner following a book for creating iPhone apps.

One of the steps was writing "UISwitch *whichSwitch = whichSwitch.isOn;" and I was just curious as to where "isOn" came from?

In the documentation:

on
A Boolean value that determines the off/on state of the switch.

@property(nonatomic, getter=isOn) BOOL on

What does that "getter=isOn" part mean? My ultimate reason for asking this question is because I want to know what I should do when I come across a similar situation for different UI elements.

Oh yeah, is this like the thing where properties create a "setSomething" mutator and "something" accessor? Except that for booleans it is "isOn" and "on"?

Thanks.

Answer 1

Properties are basically shorthand for generating methods later (the actual creation is done by @synthesize directives in the implementation file). The getter=isOn inside the @property does indeed mean that the getter method has the name isOn.

Properties by default will create a getter with the same name as the ivar and a setter with set prepended. Changing the getter name (or its setter, with the setter= syntax) is all this property directive does. You should do this only for boolean or similar variables - other variables should have a getter with the same name as the variable.