Question

I’m trying to lock down my understanding of proper memory management within Objective-C.

I’ve gotten into the habit of explicitly declaring self.myProperty rather than just myProperty because I was encountering occasional scenarios where a property would not be set to the reference that I intended.

Now, I’m reading Apple documentation on releasing IBOutlets, and they say that all outlets should be set to nil during dealloc. So, I put this in place as follows and experienced crashes as a result:

- (void)dealloc {
    [self.dataModel close];
    [self.dataModel release], self.dataModel = nil;
    [super dealloc];
}

So, I tried taking out the “self” references, like so:

- (void)dealloc {
    [dataModel close];
    [dataModel release], dataModel = nil;
    [super dealloc];
}

This second system seems to work as expected. However, it has me a bit confused. Why would self cause a crash in that case, when I thought self was a fairly benign reference more used as a formality than anything else? Also, if self is not appropriate in this case, then I have to ask: when should you include self references, and when should you not?

Answer 1

I have adopted the following after seeing Apple sample code and iphone dev books.

set outlets to nil in ‘viewDidUnload’ (use SELF accessor)
release them in ‘dealloc’ (no SELF)

- (void)viewDidUnload {
    // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
    // For example: self.myOutlet = nil;
    self.button = nil
}


- (void)dealloc {
   // no SELF
   [button release];   // UI objects
   [images release];   // model objects
}