Question

I’m trying to resolve a memory leak but I can’t find any solution.

Instruments says that there is a leak in this method:

 - (void)refreshData {

 Sn0werSp33dAppDelegate *appDelegate = [[Sn0werSp33dAppDelegate alloc] init];
 NSFetchRequest *coreDataNewsFetchRequest = [[NSFetchRequest alloc] init];
 NSEntityDescription *entity = [NSEntityDescription entityForName:@"News" inManagedObjectContext:managedObjectContext];

 [coreDataNewsFetchRequest setEntity:entity];

 self.managedObjectContext = appDelegate.managedObjectContext;
 self.newsArray = [[managedObjectContext executeFetchRequest:coreDataNewsFetchRequest error:nil] mutableCopy];//Intruments says that here is the memory leak :(


 [appDelegate release];
 [coreDataNewsFetchRequest release];
 [entity release];
}

newsArray is declared in my .h as an NSMutableArray and it has a property:
@property (nonatomic, retain) NSMutableArray *newsArray;

I’ve tried many things but at all times, that things weren’t working.
I’m running XCode 3.2.5 with iPhone SDK 4.2.1 and Instruments 2.7.

Answer 1

When you do

self.newsArray = something; 

that something is retained, because you added retain to the newsArray property.

But mutableCopy also returns an object with a retain count increased by 1. So after the method finishes, your newsArray has a retain count one higher than what you really want, which is the memory leak that was detected.

Solution: Replace the line where you assign self.newsArray with

self.newsArray = [[[managedObjectContext executeFetchRequest:coreDataNewsFetchRequest error:nil] mutableCopy] autorelease];