Do I need release in the dealloc?

Question

In the book I'm studying from for iPhone dev, they utilize IBOutlet instances using the Interface Builder. An example would be a UIButton. So they add a thing in the struct like this:

 IBOutlet UIButton *whateverButton;

Then they add a @property for each of these in the .h, and a @synthesize in the .m.

Then they include a release in the dealloc of the .m. Two questions:

1. Is the release necessary? Aren't all properties already handled automatically?
2. How can I check the ref count to see what's happening, for debug purposes...?

Answer 1

Is the release necessary? Aren't all properties already handled automatically?

If the property is retained, the release is necessary. When you declare a @property and @synthesize it, all you get is the accessors, there is no special automatic behaviour in dealloc.

Also, there is nothing magical about IBOutlet – it’s just a marker for Interface Builder to see which properties you would like to appear in IB. It’s simply an empty macro, Cmd-click the IBOutlet keyword to see its definition:

#ifndef IBOutlet
#define IBOutlet
#endif

Same thing goes for IBAction which expands to void.

How can I check the ref count to see what's happening, for debug purposes...?

When I need to debug memory management, I usually simply set up a breakpoint in the dealloc method or log a string there. It is also helpful to log the retainCount of an object around the calls that might do something fishy with it.

---

It might also help to see how the @synthesize directive creates the accessors. When you declare a retained @property and ask the compiler to @synthesize them, you get something like this:

@property(retain) NSString *foo;
@synthesize foo;

- (void) foo {
    return foo;
}

- (void) setFoo: (NSString*) newFoo {
    // Try to think what would happen if this condition wasn’t
    // here and somebody called [anObject setFoo:anObject.foo].
    if (newFoo == foo)
        return;
    [foo release];
    foo = [newFoo retain];
}

This isn’t exactly the thing, but it’s close enough. Now it should be more clear why you should release in dealloc.