How to test Selectors on proxy-objects in Objective-C?

Question

Is there any way to test selectors/methods when all you have is a proxy object?

/* Proxy which may forward
 * the method to some other object */ 
id proxy = [UINavigationBar appearance];

/* This condition returns FALSE
 * despite the fact that the method would have otherwise been
 * successfully executed at its destination */
if([proxy respondsToSelector:@selector(setBarTintColor:)]){
    [proxy setBarTintColor:color];
}

Answer 1

Apparently you cannot.

The methods suggested by other answers will break easily, here's an example:

• UINavigationBar instances respond to selector setTranslucent:
• However setTranslucent: is not tagged with UI_APPEARANCE_SELECTOR in the header file

Therefore the following code

if([[UINavigationBar class] instancesRespondToSelector:@selector(setTranslucent:)]) {
    [[UINavigationBar appearance] setTranslucent:NO]; // BUM!
}

will result in a crash.

The only information about which selectors conform to UIAppearance seems to be the UI_APPEARANCE_SELECTOR macro, which is stripped at compile-time.

A runtime check doesn't look to be feasible.

---

For the sake of completeness, here's an awful (but practical) way of doing it.

@try {
    [[UINavigationBar appearance] setTranslucent:YES];
} @catch (NSException *exception) {
    if ([exception.name isEqualToString:@"NSInvalidArgumentException"])
        NSLog(@"Woops");
    else
        @throw;
}

However, this is very fragile since there's no guarantee that you're catching only the case in which the selector doesn't conform to UIAppearance.