GC and Object Creation in Interface Builder

In a project with garbage collection set to required: If I instantiate an object in Interface Builder and add it to the XIB/NIB, do I need to assign this object to some outlet to avoid it b开发者_运维知识库eing garbage-collected, or is that taken care through some other means?

Top level objects need to be assigned to an outlet somewhere or attached to some variable using the top level objects array when instantiating the nib. Otherwise, they are useless to you anyway. A view which is contained within another view or window is in that views instance variables so it is safe.

I just built a small test project. With GC, the object created through Interface Builder gets collected soon afterwards. So the answer to the question is: yes.

I did a bit more testing:

With classical reference counting this does not happen. This is possibly what one would expect, but it is also probably a memory leak. Not sure here. (If not, and the NIB/XIB-contained objects get released when the file's owner is release, e.g., then this would constitute a significant difference in behavior between GC and classical RC.)

With ARC enabled, I did not find a way to tell. There is probably some function I could put a breakpoint on and wait for the specific object fly by.

Edit:

I reviewed the documentation, and it states it quite clearly. Missed that the first time around:

You typically need strong references to top-level objects to ensure that they are not deallocated; you don’t need strong references to objects lower down in the graph because they’re owned by their parents, and you should minimize the risk of creating strong reference cycles.

From: Resource Programming Guide, Managing the Lifetimes of Objects from Nib Files