How to perform Callbacks in Objective-C

Question

How to perform call back functions in Objective-C?

I would just like to see some completed examples and I should understand it.

Answer 1

Here's an example that keeps the concepts of delegates out, and just does a raw call back.

@interface Foo : NSObject {
}
- (void)doSomethingAndNotifyObject:(id)object withSelector:(SEL)selector;
@end

@interface Bar : NSObject {
}
@end

@implementation Foo
- (void)doSomethingAndNotifyObject:(id)object withSelector:(SEL)selector {
    /* do lots of stuff */
    [object performSelector:selector withObject:self];
}
@end

@implementation Bar
- (void)aMethod {
    Foo *foo = [[[Foo alloc] init] autorelease];
    [foo doSomethingAndNotifyObject:self withSelector:@selector(fooIsDone:)];
}

- (void)fooIsDone:(id)sender {
    NSLog(@"Foo Is Done!");
}
@end

Typically the method -[Foo doSomethingAndNotifyObject:withSelector:] would be asynchronous which would make the callback more useful than it is here.