Question

I am working on a project where I have a class which has UIView property. I also define a class which is a subclass of UIView which defines a certain method. If I have the following code, I get a warning when I build:

// In this example, myView is UIView property which *may* contain a UIView or 
// my subclassed-UIView which has the myMethod method
if([myView respondsToSelector:@selector(myMethod)]){
   [myView myMethod]
}

The warning is “UIView may not respond to ‘-myMethod'”. The warning obviously doesn’t stop the app from being built, but I am just trying to figure out how to deal with it. Is this the correct way to do this? Is there a way to stop this warning?

Answer 1

The warning is only because the compiler doesn’t know if that view is your custom subclass. Of course, at runtime it will work fine, since it will be a subclass. You have two options to fix it:

[myView performSelector:@selector(myMethod)];

(So the compiler doesn’t check the method call at all)

Or, better:

[(MyViewClass *)myView  myMethod];

That way the compiler acts as if the object really is your view subclass (after you performing the check of course).

For that matter, it might make sense to check for your class rather than the method:

if ([myView isKindOfClass:[MyViewClass class]]) { ...