GCD常用的函数

1、延迟函数

//延迟执行

//[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(task) userInfo:nil repeats:YES];

//[self performSelector:@selector(task) withObject:nil afterDelay:3.0];

dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

//GCD延迟执行

/*

第一个参数:表示从什么时候开始计时 DISPATCH_TIME_NOW:现在

第二个参数:间隔的时间

第三个参数:队列,决定block在哪个线程中调用,只有当队列是主队列的时候才在主线程调用

第四个参数:

*/

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), queue, ^{

NSLog(@"----GCD---%@",[NSThread currentThread]);

});

2、栅栏函数

//1.创建并发队列

dispatch_queue_t queue = dispatch_queue_create("www.yifuj.com", DISPATCH_QUEUE_CONCURRENT);

//2.使用异步函数添加任务

dispatch_async(queue, ^{

for (NSInteger i = 0; i<10; i++) {

NSLog(@"download 1--%zd-%@",i,[NSThread currentThread]);

}

});

dispatch_async(queue, ^{

for (NSInteger i = 0; i<10; i++) {

NSLog(@"download 2--%zd-%@",i,[NSThread currentThread]);

}

});

dispatch_async(queue, ^{

for (NSInteger i = 0; i<10; i++) {

NSLog(@"download 3--%zd-%@",i,[NSThread currentThread]);

}

});

//栅栏函数:控制队列中任务的执行顺序,前面的所有任务执行完毕之后执行栅栏函数,自己执行完毕之后再之后后面的任务

dispatch_barrier_async(queue, ^{

NSLog(@"++++++++++++++++++++++++++");

});

dispatch_async(queue, ^{

for (NSInteger i = 0; i<10; i++) {

NSLog(@"download 4--%zd-%@",i,[NSThread currentThread]);

}

});

dispatch_async(queue, ^{

for (NSInteger i = 0; i<10; i++) {

NSLog(@"download 5--%zd-%@",i,[NSThread currentThread]);

}

});