When to release and when to autorelease

The general rule for when to call -release or -autorelease are simple:

• You always -autorelease, unless you are writing -dealloc
• In -dealloc you should always use -release.
• You may -release in -init if you are returning nil

So you also -autorelease in -finalize

It's not bad to -autorelease in -dealloc it is just wasteful.

The add to container then release idiom

The advantage of this code:

obj = [Foo new];
[container addObject:obj];
[obj release];

vs.

obj = [Foo instantiate];
[container addObject:obj];

are, that a -release can be a bit faster than -autorelease. If you are writing a container, which could hold a large quantity of objects, it may pay off.

What can go wrong here ?

A problem is that you can all to easily steer into a situation like this:

+ (id) newFooWithContainer:(NSMutableArray *) array
{
   id   obj;

   obj = [Foo new];
   [array addObject:obj];
   [obj release];

   ...

   return( obj);
}

What happens when array is nil ?