在对象的类的方法中释放对象是否可以接受

Question

Is it acceptable for a instance method of a class to release itself?

ie to have a method that calls:

[self release]

Assume that my code is not going to access self after calling [self release]

Answer 1

You should only do this if you've done something like

[self retain];

But it's unclear why you would do that. The Cocoa Memory Management Documentation might help

Answer 2

While I doubt that immediately after your release, memory would move much, keep in mind that the code that your [self release] is in, resides in a memory block inside your object, self. Thus, it is possible that after returning from [self release], you end up in code that is no longer allocated and is being written over by some other process. Can't say for sure how probable that is, but it seems possible.

Answer 3

I have used this technique once before, for a similar situation (standalone object handling response from a web delegate that may outlive the view that launched the request).

It does work, but is actually rather tricky to get right. Since then I have found that using NSOperations in an NSOperationQueue is a much more solid and well-understood approach to encapsulating background actions that run independent of the requestors. Usually when an operation is done a notification is sent out on the main thread informing whatever caller might still be around that data is ready for pickup.

Plus for simple remote requests you can use the simpler synchronous URL calls in your Operation since they run in a separate thread and will not block the main thread while data is incoming (handy when fetching small images from URL's, for example).

Answer 4

Is it acceptable for a instance method of a class to release itself?

ie to have a method that calls:

[self release]

Assume that my code is not going to access self after calling [self release]

First, I would want to have a really good reason to release myself. The only time I've done it is in a singleton that I dump to free up large chunks of memory on an iPhone. This is a rare event.

Your code is part of the class object. Hence, it is not really a problem to call [self release]. Of course, you are much safer, from an encapsulation perspective, if you call [self autorelease]. At least then, if someone up the call chain calls your methods, you don't cause an exception.

Andrew

Answer 5

You can do it. It works. It is a bit dangerous, especially since optimizing compilers can rearrange your code in ways you didn't intend them to.

A little bit safer is to call [self autorelease], which will release the current object at some point in the near future (the next time through the runloop typically) rather than right away.