Question

I made a getter do this:

@synthesize sheet = _sheet;

-(CCSpriteBatchNode *)sheet {
    if (!_sheet) {
        _sheet = [CCSpriteBatchNode batchNodeWithFile:@"image.png" capacity:500];
        [self addChild:_sheet];
    }
    return _sheet;
}

But my question is, what is the proper way to declare this property?

in my interface, I have done:

@property (readonly, unsafe_unretained) CCSpriteBatchNode *sheet;

because I thought, since this is “readonly”, I don’t need a strong reference to it– but then I got confused and thought– wait does that mean there’s a chance it will get released, and this should be strong? I used unsafe_unretained instead of weak to have iOS4 support…

Answer 1

“readonly” property means that there is no setter function to modify the value of the property. That has nothing to do with “strong” versus “weak/unsafe_unretained”.

You should declare the property “strong” to make sure that the object is not released while somebody is using it.

In your particular case, self probably retains _sheet because of [self addChild:_sheet], so _sheet will exist at least as long as self. But if you declare the property as “unsafe_unretained” and another class gets the value via

CCSpriteBatchNode *theSheet = yourWhatEver.sheet;

then theSheet will be an invalid pointer as soon as yourWhatEver is deallocated.