Cancel [self performSelector:... withObject:nil afterDelay:20];

I call method sr in viewDidLoad with below code,how can i cancel it before that method sr will call?

[self performSelector:@selector(sr) withObjec开发者_开发知识库t:nil afterDelay:20]; 

[NSObject cancelPreviousPerformRequestsWithTarget:self
                                         selector:@selector(sr)
                                           object:nil];

Please read the documentation. :) The documentation for -performSelector:withObject:afterDelay: points you to the methods for canceling a queued perform request.