iOS Core Data how can it leak?

Question

Hello

I was analyzing my app with leaks, and i observe that some core data entity is leaking, how can a NSManagedObject leak? I thought it was managed by the operating system? Are there known leaks in core data? The line that Leaks says causes the leak is

NSMutableArray *e=[NSMutableArray  arrayWithArray:[[user videos] allObjects]];
    //the line above ^ is pointed to by leaks as generating a leak
for(VideoEntity * v in e)
{
    UploadThread *ut= [[UploadThread alloc] init];
    [ut setVideoEntity:v];
    [threads addObject:ut];
    [ut release];
}

Where user is a managed object which contains VideoEntity as a to-many relationship, and I assign the VideoEntitys to some threads to operate on...Leaks says VideoEntity is leaking.

Does anyone have any input?

Thanks

Daniel

Answer 1

UploadThread may be retaining it and never releasing it. Yes, NSManagedObjects can leak. They're just objects. They are part of the same memory management that the rest of the system uses.

Answer 2

Managed Objects that have relationships have implicit retain cycles (i.e., both sides of the relationship retain their objects). Once you fault in a relationship, you create this retain cycle. To break it, you need to call -[ManagedObjectContext refreshObject:mergeChanges:] to re-fault the object and break the retain cycles.

For more information, see the memory manage section of the Core Data Programing Guide.

Also, just as a note, if you're sending instances of managed objects across threads, you shouldn't be. You should use the object id instead (these are thread safe).