ios - NSOperationQueue 如何等待两个异步操作？

Question

如何让 NSOperationQueue(或其他任何东西)等待两个带有回调的异步网络调用？流程需要看起来像这样

Block Begins {
    Network call with call back/block begins {
        first network call is done 
    }
}
Second Block Begins {
    Network call with call back/block begins {
        second network call is done 
    }
} 

Only run this block once the NETWORK CALLS are done {
    blah
}

这是我目前所拥有的。

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
__block NSString *var;


[queue addOperation:[NSBlockOperation blockOperationWithBlock:^{
   [AsyncReq get:^{
       code
    } onError:^(NSError *error) {
       code
    }];
}]];

[queue addOperation:[NSBlockOperation blockOperationWithBlock:^{
   [AsyncReq get:^{
       code
    } onError:^(NSError *error) {
       code
    }];
}]];
[queue waitUntilAllOperationsAreFinished];
//do something with both of the responses

Answer 1

你必须使用NSOperation Queue吗？以下是使用调度组执行此操作的方法:

dispatch_group_t group = dispatch_group_create();

dispatch_group_enter(group);
[AsyncReq get:^{
    code
    dispatch_group_leave(group); 
} onError:^(NSError *error) {
    code
    dispatch_group_leave(group);
}];


dispatch_group_enter(group);
[AsyncReq get:^{
    code
    dispatch_group_leave(group); 
} onError:^(NSError *error) {
    code
    dispatch_group_leave(group);
}];

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    NSLog(@"Both operations completed!")
});