How is retain setter implemented with @synthesize?

Question

I have the following in the header:

@property (nonatomic, retain) UIView *overlay;

And in the implementation:

@synthesize o         


        

Answer 1

As your property is defined with (retain) any instance you set using the synthesized setter (via the self.overlay syntax) will automatically be sent a retain message:

// You're alloc'ing and init'ing an object instance, which returns an 
// instance with a retainCount of 1.
UIView *tempOverlay = [[UIView alloc] initWithFrame:CGRectMake(160.0f, 70.0f, 150.0f, 310.0f)];

// The overlay property is defined with (retain), so when you assign the new 
// instance to this property, it'll automatically invoke the synthesized setter, 
// which will send it a retain message. Your instance now has a retain count of 2.
self.overlay = tempOverlay;

// Send a release message, dropping the retain count to 1.
[tempOverlay release];

If you were to do:

self.overlay = [[UIView alloc] initWithFrame:CGRectMake(160.0f, 70.0f, 150.0f, 310.0f)];

Your overlay would have a retain count of two, which will likely lead to a leak at some point in your application.