Question

When I perform a [NSString release] or [NSArray release] or [NSMutableArray release], what happens?
Does the memory became wiped out?
Or just pushed on the stack and dropped from the heap, or vise versa?

If I just want to dump memory when I am done with it, is “release” the best thing to use?

I am dealing with many matrices and don’t want them sticking around using memory…

thanks

Answer 1

When I perform a [NSString release] or [NSArray release] or
[NSMutableArray release], what happens?

The retainCount of the instance that you call release on is decremented. If it reaches 0 as a result of your call, then the instance will be deallocated.

Does the memory became wiped out? Or just pushed on the stack and dropped from the heap, or vise versa?

Not necessarily. The memory may become wiped out (in the sense that it no longer contains a valid object instance and may be overwritten by other things) once the retainCount reaches 0 (or less if you over-release something), but this is not guaranteed to happen immediately upon your call to release. The released instance may in fact stick around for quite awhile, if it is associated with an NSAutoreleasePool that is not drained frequently or if someone else has called retain on it.

If I just want to dump memory when I am done with it, is “release” the
best thing to use?

In general, yes. If you want really low-level control of things, you can also use malloc() and free() instead, which will release memory more immediately than calling release will.