延迟执行一个函数,可以使用`[self performSelector:@selector(delayMethod:) withObject:nil afterDelay:1];`也可以用GCD的dispatch_after来实现 // 延迟2秒执行:
double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
// code to be executed on the main queue after delay
});