Question

I have two view controllers and nibs. I populated one view controller with a toggle switch and declared this in its header file:

@public UISwitch *toggleSwitch;

and exposed it as a property like this:

@property (nonatomic,retain) IBOutlet UISwitch *toggleSwitch;

I also connected the switch with toggleSwitch outlet. Now I want to use this toggleSwitch field in my other view controller, how do I do that? Isn’t using @public in the field declaration enough? Please help. Thank you.

Answer 1

No problem at all. Just use the switch like this:

vcWhereYouDeclaredTheSwitch.toggleSwitch.on = YES;

or

BOOL test = [vcWhereYouDeclaredTheSwitch.toggleSwitch isOn];

inside your other view controller.

Here are some general thoughts about propertys:

• Memory management : Behind the scenes it will create a setter which creates the variable with correct memory management. It will save you some headaches because you can easily see how the memory management is done (strong/weak and retain/copy/assign).

• Accessibility from other classes: if you declare your @property in the .h and @synthesize it in the .m you ivar will be public readable and writeable. You can prevent this with a privat class extension. You even can declare a @property public readonly and declare them internally readwrite via a privat class extension.
  Eg: a private property

   // [In the implementation file]  
   @interface MyClass ()  
   @property (nonatomic, retain) NSMutableArray* someData; // private!!   
   @end  

   @implementation MyClass @synthesize someData   
   @end

• Custom getter and setter: If you like you can still write custom getter and setters and you can even just write a getter or setter and let the other one automatically @synthesize. And you can write custom logic into such a getter and setter e.g. you can reload a tableview after a @property has changed.

• Automatic Key-Value-Observing (KVO) compliant: If you use or planning to use KVO you get it basically for free by just declaring the property. Nothing else need to be done!

• If you need you iVar to be public it is simpler to write one @property than writing a getter and setter for a iVar

• With a @property you do not need to declare in iVar (in iOS and 64bit Mac Os X applications). You can do it via the @synthesize:

    @synthesize myiVar = _myIvar;