变更记录

序号	录入时间	录入人	备注
1	2015-03-02	Alfred Jiang	-
2	2015-12-18	Alfred Jiang	-

方案名称

时间 - 延时执行解决方案

关键字

时间 \ 延时执行

需求场景

部分需要延时等待的操作

参考链接

博客园 - iOS延时执行的几种方法

详细内容

直接使用 performSelector ```objective-c
(void)checkRefreshCatalogViewData { [catalogView performSelector:@selector(refreshDataAfterFiveMinute) withObject:nil afterDelay:kRefreshCatalogViewDelayTime]; }

//对于代码中调用performSelector产生延时操作的代码，如果不是通过category方式定义，要在dealloc函数里面用cancelPreviousPerformRequestsWithTarget取消。因为不取消的话，如果页面在延时的时间内退出，将因为找不到执行函数而崩溃。

(void)dealloc { [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(refreshDataAfterFiveMinute) object:nil]; [super dealloc]; } ```
Block + performSelector ```objective-c @implementation NSObject (PerformBlockAfterDelay)
(void)performBlock:(void (^)(void))block
```
    afterDelay:(NSTimeInterval)delay
```
{ block = [block copy]; [self performSelector:@selector(fireBlockAfterDelay:)
```
         withObject:block
         afterDelay:delay];
```
}
(void)fireBlockAfterDelay:(void (^)(void))block { block(); }

@end

3. GCD
```swift
//Swift 解决方案
func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

//Objective-C 解决方案
- void RunBlockAfterDelay(NSTimeInterval delay, void (^block)(void))
{
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC*delay),
                   dispatch_get_main_queue(), block);
}

用 animation 的 completion 参数 (不推荐)

[UIView animateWithDuration:0.0
                   delay:5.0
                 options:UIViewAnimationOptionAllowUserInteraction
              animations:^{
                  //
              }
              completion:^(BOOL finished) {
                  //do stuff here
              }];

使用 NSOperationQueue ，在应用程序的下一个主循环执行 (不推荐)
```
[[NSOperationQueue mainQueue] addOperationWithBlock:aBlock];
```
这个和调用 performSelector: with afterDelay of 0.0f 等价