GCD之死锁

GCD相当好用，但用不好就会死锁,始终要记着这样一句秘籍：

不要在串行队列放dispatch_sync、dispatch_apply

下面看几个例子

// 防死锁秘籍：不要在串行队列放dispatch_sync、dispatch_apply

   // 死锁  主线程调用dispatch_apply

    dispatch_async(dispatch_get_main_queue(), ^{

        dispatch_apply(5, dispatch_get_main_queue(), ^(size_t i) {

            NSLog(@"%ld",i);

            NSLog(@"%d",55);

        });

      });

    NSLog(@"%d",999);

    //死锁 主线程调用dispatch_apply

    dispatch_apply(5, dispatch_get_main_queue(), ^(size_t i) {

        NSLog(@"%ld",i);

        NSLog(@"%d",777);

    });

   //不死锁

    dispatch_queue_t queue=  dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_apply(5, queue, ^(size_t i) {

        NSLog(@"%ld",i);

         NSLog(@"%d",66);

    });

    NSLog(@"%d",88);

    //不死锁

    dispatch_async(queue, ^{

        dispatch_apply(5, dispatch_get_main_queue(), ^(size_t i) {

            NSLog(@"%ld",i);

        });

    });

//    //不死锁

    dispatch_async(queue,^{

        dispatch_sync(dispatch_get_main_queue(), ^{

            NSLog(@"test");

        });

    });

    //死锁

    dispatch_sync(queue,^{

        dispatch_sync(dispatch_get_main_queue(), ^{

            NSLog(@"test");

        });

    });