四个简单易用的demo，关于iOS定时器和延时的，非常好用。

[objc] view plain copy

/** 
 ** delay 不可重复 
 **/  
- (void)timerMethodA  
{  
    [self performSelector:@selector(methodAEvent)  
               withObject:nil  
               afterDelay:2.0f];//延时时间  
}  
  
- (void)methodAEvent  
{  
    NSLog(@"-- method_A");  
}  

[objc] view plain copy

/** 
 ** dispatch_time 可重复 
 **/  
- (void)timerMethodC  
{  
    __block int i = 0;  
    CGFloat duration = 1.0f;   //间隔时间  
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);  
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);  
      
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, duration * NSEC_PER_SEC, 0);  
    dispatch_source_set_event_handler(timer, ^{  
          
        i++;  
        if (i > 5) {  
            dispatch_source_cancel(timer);  //执行5次后停止  
            NSLog(@"-- end");  
        }else{  
            NSLog(@"-- Method_C i:%d", i);  
        }  
    });  
    dispatch_resume(timer);  
}  

[objc] view plain copy

/** 
 ** dispatch_time 不可重复 
 **/  
- (void)timerMethodD  
{  
    CGFloat delayTime = 2.0f;   //延时时间  
    dispatch_time_t timer = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayTime *NSEC_PER_SEC));  
    dispatch_after(timer, dispatch_get_main_queue(), ^{  
        NSLog(@"-- Method_D time:%@", [NSDate date]);  
    });  
                                            
}