Question

Note: This other question seems relevant but it’s not: When does an associated object get released?

I’m adding a second description to a UIView instance as follows:

- (void) setSecondDescription:(UIView*)view description2:(NSString*)description2 {
    objc_setAssociatedObject (view,&key,description2,OBJC_ASSOCIATION_RETAIN);
}

- (NSString*) secondDescription:(UIView*)view {
    return (id)objc_getAssociatedObject(view, &key);   
}

If the UIView deallocs, will the associated description 2 get dealloced? Is there any way to get this to happen automatically?

Answer 1

If you want to actually see the description of the entire dealloc timeline, look at WWDC 2011, Session 322, 36:22. However, here’s the basic rundown (I wanted to remember it, so this is an actual comment in a piece of my code).

Note, that the associated objects are released at the end of the life cycle.

// General Information
// We take advantage of the documented Deallocation Timeline (WWDC 2011, Session 322, 36:22).
// 1. -release to zero
//     * Object is now deallocating and will die.
//     * New __weak references are not allowed, and will get nil.
//     * [self dealloc] is called
// 2. Subclass -dealloc
//     * bottom-most subclass -dealloc is called
//     * Non-ARC code manually releases iVars
//     * Walk the super-class chain calling -dealloc
// 3. NSObject -dealloc
//     * Simply calls the ObjC runtime object_dispose()
// 4. object_dispose()
//     * Call destructors for C++ iVars
//     * Call -release for ARC iVars
//     * Erase associated references
//     * Erase __weak references
//     * Call free()