Question

I tend to do everything with Interface Builder and IBOutlet, so that when I want to modify user interface I use to declare a variable in UIViewController, for example:

@property(nonatomic,retain) IBOutlet MyView *myView;

connect it trough Interface Builder and recall in my code using the outlet, then I can access all the other outlet in myView:

UILabel *label = myView.theLabel;

Considering that MyView is very often my main view, I could also do:

UILabel *label = (MyView*)self.view.theLabel;

the syntax is quite long, but this allow me to declare less variable in the .h file and (in my opinion) keep code cleaner, for example with a macro this could become:

#define MV (MyView*)self.view

UILabel *label = MV.theLabel;

which I found to be much more nice to read and maintain.
The point is that I would always do a casting, using iOS 5 what’s the cost in terms of performance ? Considering the UIKit is already a layer on top of something else is UIView object casting somewhat different or more expensive ?
Does the compiler do some kind of optimizations especially with the new arc compiler ?

thanks

Answer 1

Casting happens at compile time, and as such has absolutely no runtime cost.

Sidebar: This way of using defines still strikes me as a bit iffy, but hey, if it works for you…

Edit: The issue you are describing is a result of conflating the purposes of the classes in your code: MyView should not need to have any outlets to speak of; keeping track of all of that jazz is the job of the view controller.

In other words; you probably don’t want self.view.label; but rather self.relevantNameForTheLabel.