ios - AFNetworking-2 waitUntilFinished 不工作

Question

我知道有 another similar question ，但它适用于旧版本的 AFNetworking，并且无论如何都没有真正回答它。

我有以下代码:

AFHTTPRequestOperationManager* manager = [AFHTTPRequestOperationManager manager];
manager.securityPolicy.allowInvalidCertificates = YES;
manager.requestSerializer = [AFJSONRequestSerializer serializer];
[manager.requestSerializer setAuthorizationHeaderFieldWithUsername: currentUser() password: currentPassword()];
__block NSDictionary* response = nil;
AFHTTPRequestOperation* operation = [manager
    GET: @"https://10.20.30.40:8765/foobar"
    parameters: [NSDictionary dictionary]
    success:^(AFHTTPRequestOperation* operation, id responseObject){
        response = responseObject;
        NSLog(@"response (block): %@", response);
    }
    failure:^(AFHTTPRequestOperation* operation, NSError* error){
        NSLog(@"Error: %@", error);}
];
[operation waitUntilFinished];
NSLog(@"response: %@", response);
...

如果我运行它，我将在我的日志中看到的是:

2013-12-09 09:26:20.105 myValve[409:60b] response: (null)
2013-12-09 09:26:20.202 myValve[409:60b] response (block): {
    F00005 = "";
    F00008 = "";
    F00013 = "";
}

在waitUntilFinished 之后 的NSLog 首先触发。我预计它会第二次开火。我错过了什么？

Answer 1

几个想法:

1. 问题是waitUntilFinished 将等待核心网络操作完成，但不会等待成功 或失败完成 block 。如果你想等待完成 block ，你可以使用信号量:

   __block NSDictionary* response = nil;
   
   dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
   
   manager.completionQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
   
   AFHTTPRequestOperation* operation = [manager GET: @"https://10.20.30.40:8765/foobar"
                                         parameters: [NSDictionary dictionary]
                                            success:^(AFHTTPRequestOperation* operation, id responseObject){
                                                response = responseObject;
                                                NSLog(@"response (block): %@", response);
                                                dispatch_semaphore_signal(semaphore);
                                            }
                                            failure:^(AFHTTPRequestOperation* operation, NSError* error){
                                                NSLog(@"Error: %@", error);
                                                dispatch_semaphore_signal(semaphore);
                                            }];
   
   NSLog(@"waiting");
   dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
   // [operation waitUntilFinished];
   NSLog(@"response: %@", response);
   

   或者，您可以将其包装在您自己的并发 NSOperation 子类中，在 AFHTTPRequestOperation 完成 block 中发布 isFinished，消除 进程中的信号量。

   注意，如果在主队列上执行信号量，请确保指定 completionQueue因为，在没有它的情况下，AFNetworking 默认将完成处理程序分派(dispatch)到主队列，您可能会死锁。

2. 顺便说一句，你永远不应该阻塞主队列(糟糕的用户体验，你的应用程序可能会被看门狗进程杀死，等等)，所以如果你从主队列这样做，我会劝阻waitUntilFinished 或信号量的使用。最好从完成 block 中启动任何你需要的东西，让主队列在这个异步网络操作正在进行时继续执行，例如:

   [activityIndicatorView startAnimating];
   
   AFHTTPRequestOperation* operation = [manager GET: @"https://10.20.30.40:8765/foobar"
                                         parameters: [NSDictionary dictionary]
                                            success:^(AFHTTPRequestOperation* operation, id responseObject){
   
                                                // do whatever you want with `responseObject` here
   
                                                // now update the UI, e.g.:
   
                                                [activityIndicatorView stopAnimating];
                                                [self.tableView reloadData];
                                            }
                                            failure:^(AFHTTPRequestOperation* operation, NSError* error){
   
                                                // put your error handling here
   
                                                // now update the UI, e.g.:
   
                                                [activityIndicatorView stopAnimating];
                                            }];
   
   // NSLog(@"waiting");
   // dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
   // // [operation waitUntilFinished];
   // NSLog(@"response: %@", response);
   

---

听起来您想让您的模型让 UI 在模型对象完成更新后进行任何必要的更新。因此，您可以使用自己的 block 参数，以便 View Controller 可以告诉模型对象在完成时做什么(而不是使用 waitUntilFinished 或信号量来使网络操作阻塞主队列)。例如，假设您的模型有这样的方法:

- (void)updateModelWithSuccess:(void (^)(void))success failure:(void (^)(NSError *error))failure
{
    AFHTTPRequestOperationManager* manager = [AFHTTPRequestOperationManager manager];
    manager.securityPolicy.allowInvalidCertificates = YES;
    manager.requestSerializer = [AFJSONRequestSerializer serializer];
    [manager.requestSerializer setAuthorizationHeaderFieldWithUsername: currentUser() password: currentPassword()];
    AFHTTPRequestOperation* operation = [manager GET: @"https://10.20.30.40:8765/foobar"
                                          parameters: [NSDictionary dictionary]
                                             success:^(AFHTTPRequestOperation* operation, id responseObject){

                                                 // do your model update here

                                                 // then call the success block passed to this method (if any),
                                                 // for example to update the UI

                                                 if (success)
                                                     success();
                                             }
                                             failure:^(AFHTTPRequestOperation* operation, NSError* error){
                                                 NSLog(@"Error: %@", error);

                                                 // if caller provided a failure block, call that

                                                 if (failure)
                                                     failure(error);
                                             }];
}

然后你的 View Controller 可以做类似的事情:

[modelObject updateModelWithSuccess:^{
    // specify UI updates to perform upon success, e.g.
    // stop activity indicator view, reload table, etc.
} failure:^(NSError *error){
    // specify any UI updates to perform upon failure
}]

最重要的是，您的代码可以使用 AFNetworking 使用的相同样式的完成 block 。如果您希望模型将信息传回，您可以向完成 block 本身添加额外的参数，但我认为以上说明了基本思想。