respondsToSelector fails for appearance proxy

ios5, ios6, objective-c, uiappearance, xcode

Solution

Don't check the appearance proxy. You can never rely on that, since it's a proxy. Instead, directly check the item that has the new method, in this case, the `UIBarButtonItem`:

BOOL hasNewMethod = [UIBarButtonItem instancesRespondToSelector:@selector(setBackgroundImage:forState:style:barMetrics:)];
if( hasNewMethod )
  NSLog(@"Running iOS 6 with new method");
else
  NSLog(@"Current OS doesn't support method...");

Problem

I’m trying to detect an iOS 6-specific appearance method, by running `respondsToSelector` on the `[UIBarButtonItem appearance]`. However, it always returns `NO` for me, whatever selector I specify: ``` // Should show NOPE in iOS 5, YEP in iOS 6. Shows NOPE always NSLog(@"%@", [[UIBarButtonItem appearance] respondsToSelector:@selector(setBackgroundImage:forState:style:barMetrics:)] ? @"YEP" : @"NOPE"); // Should show YEP in both iOS 5 and iOS 6. Shows NOPE always NSLog(@"%@", [[UIBarButtonItem appearance] respondsToSelector:@selector(setBackgroundImage:forState:barMetrics:)] ? @"YEP" : @"NOPE"); ``` Actually using those methods works fine on their respective versions of iOS, but I can’t seem to detect which one is available to me. So how do I properly do that?

Original source