Question

I have a problem that I solved using delegates, but now I am thinking I may have made a mistake.

This is what I want to do.

I have a class that runs on a delay. When it is done it has a finished delegate that it calls.

Now I have the main class that creates two of these delay classes.

I don’t want them to both be handled by the same isfinished method in the main class. I want to use two different ones.

However I believe with the protocol method of creating delegates that this will not work for me.

Is there a way around this?

delayclass setdelegates MainclassFunction1
delayclass setdelegates MainclassFunction2

Answer 1

Using delegates doesn’t seem like the correct approach to me; they’re generally used for augmenting behavior. What sounds most appropriate here is the target/selector pattern, like NSTimer.

@interface MyObject : NSObject {
@private
    id target;
    SEL selector;
}
@property(assign) id target;
@property SEL selector; /* The selector must return void and accept one argument, which is the MyObject instance that invoked the method. */
@end

@implementation MyObject
- (void)notifyTarget {
    [[self target] performSelector:[self selector] withObject:self];
}
@synthesize target;
@synthesize selector;
@end

This is generally the cleanest approach since the delegate callback doesn’t need to disambiguate the sender. Using notifications seems like too much overhead for a problem in this domain.