GCD 常用的几个方法

GCD 常用的几个方法

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1、在主线程中延迟执行某动作，不会卡主主线程

double delayInSeconds = 1.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
 dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
     //执行事件
});  

2、延时重复执行

NSTimeInterval period = 0.02; //设置时间间隔
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_walltime(NULL, 0), period * NSEC_PER_SEC, 0); //每秒执行
dispatch_source_set_event_handler(_timer, ^{
           //在这里执行事件
});
dispatch_resume(_timer); 

3、在子线程中执行某动作，不会卡主整个线程

//开启子线程
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    //此处已经是子线程
    //do something

    //回到主线程执行
    dispatch_async(dispatch_get_main_queue(), ^{
      NSLog(@"主线程！！");
    });
});

4、单程锁，单例

+ (id)sharedInstance {
    static XXClass *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (!sharedInstance) {
            sharedInstance = [[self alloc] init];
        }
    });
    return sharedInstance;
}