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;}