dispatch_set_target_queue usage not correct

[haifenghuang]

In initWithCacheDirectory method of EGOCache.m file, the dispatch_set_target_queue's usage is not correct.

- (instancetype)initWithCacheDirectory:(NSString*)cacheDirectory {
    if((self = [super init])) {
        _cacheInfoQueue = dispatch_queue_create("com.enormego.egocache.info", DISPATCH_QUEUE_SERIAL);
        dispatch_queue_t priority = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
        dispatch_set_target_queue(priority, _cacheInfoQueue);

        _frozenCacheInfoQueue = dispatch_queue_create("com.enormego.egocache.info.frozen", DISPATCH_QUEUE_SERIAL);
        priority = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
        dispatch_set_target_queue(priority, _frozenCacheInfoQueue);

        _diskQueue = dispatch_queue_create("com.enormego.egocache.disk", DISPATCH_QUEUE_CONCURRENT);
        priority = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0);
        dispatch_set_target_queue(priority, _diskQueue);

In man page of dispatch_set_target_queue, it has below statements:

The result of passing the main queue or a global concurrent queue as the first argument of dispatch_set_target_queue() is undefined.

So the usage of dispatch_set_target_queue is not correct, the correct usage should be as below:

dispatch_set_target_queue(_cacheInfoQueue, priority);
dispatch_set_target_queue(_frozenCacheInfoQueue, priority);
dispatch_set_target_queue(_diskQueue, priority);

[migrant]

Yes, I have the same question. Seems like @haifenghuang 's code is correct