Objective-C: Retain cycle
Objects in a hierarchy are created, owned and freed in a chain along the hierarchy.
In its most simple form, a retain cycle occurs when two objects keep a strong reference to each other since both objects do retain each other, making it impossible to
ARC you avoid retain cycles by declaring one of the items as a weak reference. For instance,
delegate properties should be weak. A weak reference means the property can become invalid.
@property (weak, nonatomic) id *delegate;
Another thing to consider is indirect references, ie
NSArray will retains it's contents.
From this great article, we get five rules:
- An object must never retain its parent
- No hierarchical ancestor can be retained
- "Connection" objects should not retain their target
- Use "close" methods to break cycles
- Temporary retains must be temporary