calling optional delegate methods

i created a delegate for a class

@protocol gameDelegate <NSObject>
@optional
-(void)gameStarted;
@required
@end

now in my game object i called this method:

[self.delegate gameStarted];

so now, if i initiate this object anywhere and set the delegate everything works fine until the gameStated g开发者_运维问答ets called, because its not implemented in the main object where the game object is created (because its optional).

i tried some variations of this

if(![self.delegate respondsToSelector: @selector(gameStarted)]) {
    //[self.delegate gameStarted];
}

but this is not working for me. any ideas how to make this "really" optional?

thanks in advance

Omit the negation from your if statement:

if ([self.delegate respondsToSelector:@selector(gameStarted)]) {
    ...
}

To accomplish this in swift, I recommend the following:

@objc protocol MyDelegate {

optional func optionalMethod()

}

class MyClass : MyDelegate {

// optionalMethod() does not have to be declared

}

Then to call the optional on your delegate object, simple use if delegate.optionalMethod?(){}

Checking if a delegate implements an optional method and then calling it is such a common pattern that I use a preprocessor macro SAFE_CALL that checks respondToSelector: and then calls the method.

The macro is:

#define SAFE_CALL(obj,method) \
([obj respondsToSelector:@selector(method)] ? [obj method] : nil)

and it is used like this:

SAFE_CALL(sourceDelegate, refresh)
// or 
NSString *response = SAFE_CALL(object, responseValue)

Note this version works only with methods with no parameters.

Originally it was implemented as a C function, but that causes warnings with performSelector leaks when using ARC. As a preprocessor macro it works exactly as expected.