What is the need of assigning 'nil' after releasing an object

Question

I usually release the object after use by

[myObject release];

But I found in some online tutorials that they assign a nil after releasing the object. Like

[myObject release];
myObject = nil;

Is it required?

Answer 1

It's a long-running debate as to whether setting the pointer to nil after releasing is necessary, but I come down on the side of it being a good idea.

After the object is released, the pointer you hold to it still points to the same place. If your release has taken the retain count to 0 then the object will be deallocated. If you then try and send a message to the deallocated object you'll get an EXC_BAD_ACCESS error. However, sending a message to the pointer after it's been set to nil won't error - it just won't do anything.

The other side of the argument is that if you're messaging a deallocated object it's good to know about it and fix your code to make sure it doesn't happen.

There are smart people in both camps.

Answer 2

No, it is not strictly required.
If your code is well-structured there's no need to force myObject to be equal to nil.

However it may be a good habit: release does not immediately destroy the object, just decrease the retain count. Thus it may be,that, even if you call release, the object will still be there for a while, creating problems if you try to send it messages.

Using myObject = nil; eliminate this problem, since, even if you send a message to myObject nothing will actually happen.