Question

I was wondering how you would release a singleton

+ (DSActivityView *)activityViewForView:(UIView *)addToView withLabel:(NSString *)labelText width:(NSUInteger)labelWidth;
 {
    // Not autoreleased, as it is basically a singleton:
    return [[self alloc] initForView:addToView withLabel:labelText width:labelWidth];
 }

When analysing this using the analyse tool i get the following error :
Potential leak of object on line 90. which is the line that returns.

I have tried autorelease that solves the error message problem but im not convinced its the right solution since i read that autoreleasing singletons is not good. Would someone be able to assist me in identifying how best to release this object?

Thanks

Answer 1

The reason why the analyzer gives you the warning is, basically, the method name:

+ (DSActivityView *)activityViewForView:(UIView *)addToView withLabel:(NSString *)labelText width:(NSUInteger)labelWidth;

according to Objective-C conventions, all method names starting with “create”/”new”/… return a retained object; your method falls under the category of convenience constructors, which are expected to return autoreleased objects, hence the warning.

On the other hand, you say this is a singleton, but in fact it is not. So, you could possibly end up calling this method more than once and thus have an actual leak. A basic way to make your method safer (and more singleton-like) is:

+ (DSActivityView *)activityViewForView:(UIView *)addToView withLabel:(NSString *)labelText width:(NSUInteger)labelWidth;
{
    static DSActivityView* gDSActivityViewSingleton = nil;
    if (!gDSActivityViewSingleton)
          gDSActivityViewSingleton = [[self alloc] initForView:addToView withLabel:labelText width:labelWidth];
    return gDSActivityViewSingleton;
}

This would both make the analyzer relax and give you more safety in front of the possibility of misuse of the method.