NSOperationQueue如何等待两个异步操作? [英] How can an NSOperationQueue wait for two async operations?

问题描述

如何使NSOperationQueue(或其他任何东西)等待带有回调的两个异步网络调用?流程需要看起来像这样

How can I make an NSOperationQueue (or anything else) wait for two async network calls with callbacks? The flow needs to look like this

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
}

这是我到目前为止所拥有的.

Here's what I have so far.

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

推荐答案

是否必须使用NSOperation Queue?这是通过调度组实现的方法:

Do you have to use NSOperation Queue? Here's how you can do it w/ a dispatch group:

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!")
});

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