What's the proper way of passing an argument to NSTimer?

whats the proper way of passing an argument to NSTimer

• Im using a basic timer that calls a method which is defined as below: - (void) refresh:(id)obj { if (obj == YES) doSomething; } I want to call this method from certain areas of my code and also from a timer [NSTimer scheduledTimerWithTimeInterval:refreshInterval target:self selector:@selector(refresh:) userInfo:nil repeats:YES]; When I put YES as the argument for the userInfo parameter I get an EXEC_BAD_ACCESS error why is this? Can someone help me do this the right way so that there is no ugly casting and such? Thanks Mark

• Answer:

  The userInfo parameter must be an object; it is typed id. YES is a primitive, namely the value 1. In order to make sure the userInfo object does not get deallocated, the timer retains it. So, when you passed YES, NSTimer was doing [(id)YES retain]. Try that in your own code and see what happens. :-P As the http://developer.apple.com/iphone/library/documentation/cocoa/reference/foundation/Classes/NSTimer_Class/Reference/NSTimer.html#//apple_ref/occ/clm/NSTimer/scheduledTimerWithTimeInterval%3atarget%3aselector%3auserInfo%3arepeats%3a states, the selector you give the method must have the signature - (void)timerFireMethod:(NSTimer*)theTimer This means you can't have an NSTimer invoke just any method—not directly at least. You can make a special method with the above signature which in turn invokes any method you want though. So, say you have a method called refresh:, and you want to call it every so often, passing it YES. You can do this like so: // somewhere { [NSTimer scheduledTimerWithTimeInterval:refreshInterval target:self selector:@selector(invokeRefresh:) userInfo:nil repeats:YES]; } - (void)invokeRefresh:(NSTimer *)timer { [self refresh:YES]; } - (void)refresh:(BOOL)flag { if (flag) { // do something } }