R – Why does a Convencience Constructor or Object Factory have to care about releasing the Object

Talking of strong versus weak references makes sense in the context of a garbage collected memory management environment (where weak pointers are automatically released and cleared even if referenced). With GC enabled, all retain/release/autorelease calls are essentially do nothing operations (though the NSAutoreleasePool -drain method triggers garbage collection).

Now since you've tagged this question as iPhone related, and there's no garbage collection on iPhone, I'm assuming you're referring to regular reference counting, by strong you mean increasing the retain count of the referenced object, and by weak you mean just storing the pointer value.

The autorelease method essentially moves ownership of an object from the calling code to the current autorelease pool, you can think of the calling code calling release and the pool calling retain.

So the reference is effectively strong, but your code loses ownership and release responsibility. Object release will be called when the autorelease pool is released/drained.

The rule of thumb is that you own (and therefore must release) any object that you

• alloc (using a method starting "alloc" or "new"*)
• copy (using any method containing the word copy)
• retain explicitly yourself

*new combines an alloc and an init into one method.

Convenience methods return objects that are autoreleased. These are valid for the scope of the method you receive them in and can be passed back to a calling method (generally). If you want to keep them longer than that, you need to retain them.