Question

I’m having a memory leak in the following code. I got 87.5% of the memory leak before Instruments itself crashed. Maybe one of you can tell me what is wrong with this code. Do I need to be releasing anything in here? Thanks.

- (void)browseSSviewControllerDidFinish:(browseSSviewController *)controller {
<SNIP>
      MANAGED_OBJECT_1 = [self newFormatFromFormat:MANAGED_OBJECT_2];
<SNIP>
}

- (Format *)newFormatFromFormat:(Format *)formatToCopy {

    NSLog(@"making new format that's a copy");
    Format *thisNewFormat = [self newBlankFormat];
    [self updateFormat:thisNewFormat withNumbersFromFormat:formatToCopy];
    return thisNewFormat;
}

-(void)updateFormat:(Format *)formatToCopyTo withNumbersFromFormat:(Format *)formatToCopyFrom {
    NSLog(@"copying formats");
    formatToCopyTo.x = formatToCopyFrom.x;
    formatToCopyTo.y = formatToCopyFrom.y;
    formatToCopyTo.z = formatToCopyFrom.z;
    formatToCopyTo.a = formatToCopyFrom.a;
    formatToCopyTo.n = formatToCopyFrom.n;
    formatToCopyTo.u = formatToCopyFrom.u;
    formatToCopyTo.s = formatToCopyFrom.s;
}

- (Format *)newBlankFormat {

    NSLog(@"making new blank format");
    gfghfAppDelegate *del = (gfghfAppDelegate *)[UIApplication sharedApplication].delegate;
    NSManagedObjectContext *MOC = del.managedObjectContext;
    NSPersistentStoreCoordinator *PSC = [MOC persistentStoreCoordinator];
    NSManagedObjectModel *MOM = [PSC managedObjectModel];
    NSEntityDescription *entity = [[MOM entitiesByName] objectForKey:@"Format"];
    Format *thisNewFormat = [[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:MOC]; 
    thisNewFormat.slot = [NSNumber numberWithInt:-1];
    NSLog(@"slot = %@",thisNewFormat.slot);
    return thisNewFormat;
}

Here is the 87.5% of the leak that I was able to get out of my backtrace before Instruments crashed:

+0xc7 calll DYLD-STUB$$objc_msgSend = 87.5%

I didn’t use mutableCopy to copy my MANAGED_OBJECTs because it just didn’t work.

Answer 1

I rewrote the newBlankFormat:thisNewFormat method and used the “insertNewObjectForEntityForName:inManagedObjectContext:” convenience method of NSEntityDescription (see “Creating, Initializing, and Saving a Managed Object” in the “Creating and Deleting Managed Objects” chapter of Apple’s “Core Data Programming Guide”).

I think my problem initially that I was using “NSManagedObject alloc” with “initWithEntity:insertIntoManagedObjectContext”, which does not make an auto-released object. It would leak even when I would release it myself from another method using a “release” later on the returned value using the instance variable that got the return value from this method. However, whether or not I put in a “retain” around the malloc, the release count wasn’t being incremented I don’t believe, since it’s not a proper init function? I’m not sure why.

But I don’t care because the following revision fixed the leak, and as it turns out, is what Apple recommended to use anyway (I think I was using the old code from an example project or something).

Here is the revision that appears to have fixed the leak, in the new version of the “newBlankFormat:thisNewFormat” function:

- (Format *)newBlankFormat:(Format *)thisNewFormat {
            NSLog(@"making new blank format");
            gfghfAppDelegate *del = (gfghfAppDelegate *)[UIApplication sharedApplication].delegate;
            NSManagedObjectContext *MOC = del.managedObjectContext;
            //[MOC reset]; don't do this, it will erase MANAGED_OBJECT_2
            thisNewFormat = [NSEntityDescription insertNewObjectForEntityForName:@"Format" inManagedObjectContext:MOC]; //this is much better than using the malloc variety
            thisNewFormat.slot = [NSNumber numberWithInt:-1];
            NSLog(@"slot = %@",thisNewFormat.slot);
            return thisNewFormat;
}