iphone - performSelector:withObject:afterDelay:' not found in protocol(s)?

Question

I have this inside a class

[delegate performSelector:@selector(doStuff:) withObject:myObject afterDelay:2.0];

and I am having this error

warning: '-performSelector:withObject:afterDelay:' not found in protocol(s)

I cannot figure out what may be wrong.

any clues?

thanks.

Answer 1

Your problem is that you've declared your delegate instance variable as:

id<SomeProtocol> delegate;

Right? Well, that means that the compile-time checker is only going to look for methods in the <SomeProtocol> protocol. However, performSelector:withObject:afterDelay: is declared on NSObject. This means that you should declare the ivar as:

NSObject<SomeProtocol> * delegate;

This is saying that it must be an NSObject that conforms to <SomeProtocol>, as opposed to any object that conforms to <SomeProtocol>. This should get rid of your warning, and you don't have to do any casting.

Answer 2

Try casting the delegate to its class' type first, then invoke performSelector:withObject:afterDelay:

[(SomeClass *) delegate performSelector:@selector(doStuff:) withObject:myObject afterDelay:2.0];

Assuming that your delegate is of type id, you need to tell the runtime that the object in fact does inherit from NSObject (where the performSelector:withObject:afterDelay: method is defined) by casting it to it's class' type.