Waiting for an AFHTTPRequestOperation to complete before continuing

Question

i'm trying to make an iOS App that communicates with an API using AFHTTPClient. The first step is to authentificate the user, to do so, i use this code:

-(void)authorize
{
    NSURLRequest *request = [httpClient requestWithMethod:@"POST" path:@"login.php" parameters:@{@"login": account.username, @"passwd":account.password}];

    AFHTTPRequestOperation *operation = [httpClient HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject) {
        [httpClient setDefaultHeader:@"Token" value:[[operation.response allHeaderFields] objectForKey:@"CSRF-Token"]];
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"%@",error.localizedDescription);
    }];
    [httpClient enqueueHTTPRequestOperation:operation];
    [httpClient.operationQueue waitUntilAllOperationsAreFinished];
}

As you can see, my code gets a token from the server response and sets it as a default header for all future requests.

I then proceed to other requests using - (void)postPath:(NSString *)path parameters:(NSDictionary *)parameters success:success failure:failure

But when i used the debugger, i found out that those other requests where executed before the authorize operation was completed, therefore they failed because they didn't have the auth token. I added [httpClient.operationQueue waitUntilAllOperationsAreFinished]; but it doesn't seem to work...

Thank you for your help

Don't use `wait` until anything functions. Those block app until the network connection finishes. Just put the necessary code in your `success` block and call `displayNextView` after it's done. — Keith Smiley, Feb 18 '13 at 01:15

score 2 · Accepted Answer · answered Feb 17 '13 at 20:34

2

Use a dispatch semaphore.

-(void)authorize
{
    dispatch_semaphore_t done = dispatch_semaphore_create(0);
    NSURLRequest *request = [httpClient requestWithMethod:@"POST" path:@"login.php" parameters:@{@"login": account.username, @"passwd":account.password}];

    AFHTTPRequestOperation *operation = [httpClient HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject) {
        [httpClient setDefaultHeader:@"Token" value:[[operation.response allHeaderFields] objectForKey:@"CSRF-Token"]];
        dispatch_semaphore_signal(done);
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"%@",error.localizedDescription);
    }];
    [httpClient enqueueHTTPRequestOperation:operation];
    [httpClient.operationQueue waitUntilAllOperationsAreFinished];
    dispatch_semaphore_wait(done, DISPATCH_TIME_FOREVER);
}

Note that this will block the method from returning, so you need to make sure it's not on the main/UI thread.

answered Feb 17 '13 at 20:34

Kevin

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What do you mean by blocking the method from returning ? – Abel Feb 17 '13 at 20:45
I tried using it like this: `dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{ [api authorize]; }); [api requestMethod:@"users"];` But it still doesn't work, the requestMethod is called before – Abel Feb 17 '13 at 20:51
You have to make the subsequent requests in the same thread (or blocked by a lock/semaphore: `^{[api authorize]; [api doOtherRequests];}`. If needed, you could create a queue and just queue up methods until the authorize call is done. – Kevin Feb 17 '13 at 21:44
Ok but when will the semaphore be notified that my operation is complete ? – Abel Feb 18 '13 at 16:54
The semaphore is notified by the signal (`dispatch_semaphore_signal`). – Kevin Feb 18 '13 at 17:47

Waiting for an AFHTTPRequestOperation to complete before continuing

1 Answers1