block用法总结（随时更新）

dispatch_queue_t ：

建立方法：

dispatch_queue_t queue = dispatch_queue_create("myblockqueue",DISPATCH_QUEUE_CONCURRENT);

DISPATCH_QUEUE_CONCURRENT //并发
DISPATCH_QUEUE_SERIAL     //串行

串行的队列也就是添加进去的一个一个block是按顺序执行，好比：

    dispatch_queue_t queue = dispatch_queue_create("myblockqueue", DISPATCH_QUEUE_SERIAL);
    
    dispatch_async(queue, ^{ sleep(3); NSLog(@"1"); }); dispatch_async(queue, ^{ NSLog(@"2"); });

结果是：

1

2

而并发的队列是：

    dispatch_queue_t queue = dispatch_queue_create("myblockqueue", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(queue, ^{ sleep(3); NSLog(@"1"); }); dispatch_async(queue, ^{ NSLog(@"2"); });

结果是

2

1

还有三种队列是系统定义的队列，根据优先级别不一样有3种:

  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); //获取系统的queue

#define DISPATCH_QUEUE_PRIORITY_HIGH 2
#define DISPATCH_QUEUE_PRIORITY_DEFAULT 0
#define DISPATCH_QUEUE_PRIORITY_LOW (-2)

固然，也能够获取主线程队列