block用法总结（随时更新）

dispatch_queue_t ：

创建方法：

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，比如：

    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，根据优先级别不同有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)

当然，也可以获取主线程队列