Am 07.06.2009 um 08:45 schrieb Marc Liyanage:
With the new dot notation I sometimes use explicit types in my
IBAction methods:
- (IBAction)doSomething:(UIButton *)button ...
instead of
- (IBAction)doSomething:(id)sender ...
so I don't have to downcast "sender" to be able to use the dot
notation.
Do others do this too? Is this discouraged for some reason?
Not a good idea. The sender can be pretty much any object. It might
not be right now, but IBActions are often hooked up to several
objects, like a toolbar item, a pushbutton and a menu item. Hence the
definition as "id". By leaving it as "id" and then typecasting, the
assumption becomes explicit in the code. By having it as another type
right away, you're kind of masking the issue.
I recommend you write it as:
-(IBAction) doSomething: (id)sender
{
NSAssert( [sender isKindOfClass: [UIButton class]] );
UIButton* senderBtn = (UIButton*)sender;
// use btn here...
}
Or at least put an assert in there if you feel you need an IBAction
with a non-ID parameter type. The details of the assert are not as
important. In fact, if you can, use [sender respondsToSelector:
@selector(whateverYouAreCalling:)] or so instead of -isKindOfClass:.
The point of the assert is to make your code fail in a noticeable way
when someone breaks the assumptions it makes.
Cheers,
-- Uli Kusterer
"The Witnesses of TeachText are everywhere..."
http://www.zathras.de
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