I am adding 

```
[self performSelector:@selector(showLyrics) withObject:nil afterDelay:20];

```

but if user restart the song then the this selector should not get performed. So I just want to 
know how I can cancel that. Because after 20 second it will get invoked but I don't want that, and reschedule 

```
 [self performSelector:@selector(showLyrics) withObject:nil afterDelay:20];

```

I'v so many 

```
[self performSelector:@selector(showLyrics) withObject:nil afterDelay:2];

```

I want to cancel all those, which I've scheduled before.