I am reading the LazyTableImages code that Apple have released and they do something to this effect (in an NSOperation subclass):

- (void)dealloc {
    [myProperty release];
    [myProperty2 release];
}

- (void)main {
    //
    // Parse operation undertaken here
    //
    self.myProperty = nil;
    self.myProperty2 = nil;
}

My thinking is that they do this in case dealloc is called before setting properties to nil.

Is my thinking correct here? Are the releases unnecessary, as self.myProperty = nil effectively releases myProperty?

One thing I have noticed in this code is that they don't release all retained objects in dealloc, only some of them, which is really the cause for my confusion.

Cheers