Pfthb

Have a look at NSSelectorFromString.

 SEL selector = NSSelectorFromString(@"setError:");
 if ([self respondsToSelector:selector])

It will allow you to create a selector at runtime, instead of at compile time through the @selector keyword, and the compiler will have no chance to complain.

I think this is because for some odd reason the selector isn't registered with the runtime.

Try registering the selector via sel_registerName():

SEL setErrorSelector = sel_registerName("setError:");

if([self respondsToSelector:setErrorSelector]) 
 [self performSelector:setErrorSelector withObject:[NSError errorWithDomain:@"SomeDomain" code:1 userInfo:nil]];

I got that message to go away by #include'ing the file with the method. Nothing else was used from that file.

I realise I'm a bit late to this thread but for completeness, you can globally turn off this warning using the target build settings.

In section, 'Apple LLVM warnings - Objective-C', change:

Undeclared Selector - NO

If your class implements the setError: method (even by declaring dynamic the setter of the eventual error property) you might want to declare it in your interface file ( .h), or if you don't like to show it that way you could try with the PrivateMethods tricky trick:

@interface Yourclass (PrivateMethods)

- (void) yourMethod1;
- (void) yourMethod2;

@end

just before your @implementation , this should hide the warnings ;).

A really comfortable macro to put in your .pch or Common.h or wherever you want:

#define SUPPRESS_UNDECLARED_SELECTOR_LEAK_WARNING(code) 
_Pragma("clang diagnostic push") 
_Pragma("clang diagnostic ignored "-Wundeclared-selector""") 
code; 
_Pragma("clang diagnostic pop") 

It's an edit of this question for similar issue...

You can turn it off in Xcode like in the screenshot:

You can also cast the object in question to an id first to avoid the warning:

if ([object respondsToSelector:@selector(myMethod)]) 
 [(id)object myMethod];

Another way to avoid this warning is to make sure your selector method looks like this:

-(void) myMethod :(id) sender

Don't forget "(id) sender" if you want to accept any sender or specify a type of a sender object if you prefer.

While the correct answer likely lies in informing Xcode through imports or registering the selector that such a selector exists, in my case I was missing a semi-colon. Make sure before you "fix" the error that perhaps, the error is correct and your code isn't. I found the error in Apple's MVCNetworking sample, for instance.

I was able to get the warning to go away by adding thenothing method (disclosure: I didn't think of this but found it by googling on scheduledtimerwithtimeinterval)

 [NSTimer scheduledTimerWithTimeInterval:[[NSDate distantFuture] timeIntervalSinceNow]
 target:self
 selector:@selector(donothingatall:)
 userInfo:nil
 repeats:YES];


 [[NSRunLoop currentRunLoop] run];

 HTTPLogVerbose(@"%@: BonjourThread: Aborted", THIS_FILE);

 }
}

+ (void) donothingatall:(NSTimer *)timer

While I appreciate knowing how to hide the warning, fixing it is better and neither Sergio's nor Relkin's techniques worked for me, for unknown reasons.