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

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// 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");         });     });