Suicide: Objective-C objects calling their own -dealloc methods on themselves

Question

Is it good practice for an object in Objective-C to commit suicide? That is, for an object to declare [self dealloc] where -dealloc permits an orderly wind down as usual? What are the principal risks?

As it happens I have a specific example, a custom timer object that extends NSObject and comprises an NSTimer instance and an NSUInteger which is set to limit the number of times the timer fires. When time is up the object tells the timer to -invalidate and then commits suicide by calling its -dealloc method. As this is automatic we have no worries about having to track the object or crucially knowing when is the correct moment to deallocate it.

For a more detailed explanation see my post over here.

Answer 1

You shouldn't be calling -dealloc. Instead call [self release] so the reference count goes to 0 and let the system call -dealloc.

Answer 2

Is it good practice for an object in Objective-C to commit suicide? That is, for an object to declare [self dealloc] where -dealloc permits an orderly wind down as usual? What are the principal risks?

No.

The only time you should ever write a call to dealloc is to send dealloc to the super object in the dealloc method of one of your classes. No exceptions.

If you try to send dealloc to an object at any other time, you risk leaving other objects with dangling pointers. Don't do it.

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Should you ever send release to self? That is a different matter, but you should still follow the Memory Management Rules. If you have sent retain to self, then at some point you will need to send release to self. There is one exception which is in init, if initialisation fails you have to release self and return nil (I guess you could claim that alloc has sent retain to self).