Passing Data through NSTimer UserInfo

Question

I am trying to pass data through userInfo for an NSTimer call. What is the best way to do this? I am trying to use an NSDictionary, this is simple enough when I have Objective-C objects, but what about other data? I want to do something like this, which doesn't work as is:

- (void)play:(SystemSoundID)sound target:(id)target callbackSelector:(SEL)selector
{
    NSLog(@"pause ipod");
    [iPodController pause];
    theSound = sound;

    NSMutableDictionary *cb = [[NSMutableDictionary alloc] init];
    [cb setObject:(id)&sound forKey:@"sound"];
    [cb setObject:target forKey:@"target"];
    [cb setObject:(id)&selector forKey:@"selector"];

    [NSTimer scheduledTimerWithTimeInterval:0
                                     target:self
                                   selector:@selector(notifyPause1:)
                                   userInfo:(id)cb
                                    repeats:NO];
}

Answer 1

You have to wrap the information correctly into the dictionary:

- (void) play:(SystemSoundID)sound target:(id)target callbackSelector:(SEL)selector
{
    NSLog(@"pause ipod");
    [iPodController pause];
    theSound = sound;

    NSMutableDictionary *cb = [[NSMutableDictionary alloc] init];
    [cb setObject:[NSNumber numberWithInt:sound] forKey:@"sound"];
    [cb setObject:target forKey:@"target"];
    [cb setObject:NSStringFromSelector(selector) forKey:@"selector"];

    [NSTimer scheduledTimerWithTimeInterval:0
                                     target:self
                                   selector:@selector(notifyPause1:)
                                   userInfo:cb 
                                     repeats:NO];
    [cb release];

}

In notifyPause1:, you retrieve everything:

- (void)notifyPause1:(NSTimer *)timer {
    NSDictionary *dict = [timer userInfo];

    SystemSoundID sound = [[dict objectForKey:@"sound"] intValue];
    id target = [dict objectForKey:@"target"];
    SEL selector = NSSelectorFromString([dict objectForKey:@"selector"]);

    // Do whatever...
}

As the timer is a repeating timer, you do not need the dictionary anymore, so you can release it.