Can AFNetworking return data synchronously (inside a block)?

Solution 1:

To block the execution of the main thread until the operation completes, you could do [operation waitUntilFinished] after it's added to the operation queue. In this case, you wouldn't need the return in the block; setting the __block variable would be enough.

That said, I'd strongly discourage forcing asynchronous operations to synchronous methods. It's tricky to get your head around sometimes, but if there's any way you could structure this to be asynchronous, that would almost certainly be the way to go.

Solution 2:

I'm using semaphores to solve this issue. This code is implemented in my own class inherited from AFHTTPClient.

__block id result = nil;
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
NSURLRequest *req = [self requestWithMethod:@"GET"
                                       path:@"someURL"
                                 parameters:nil];
AFHTTPRequestOperation *reqOp = [self HTTPRequestOperationWithRequest:req
                                                              success:^(AFHTTPRequestOperation *operation, id responseObject) {
                                                                  result = responseObject;                                                                          
                                                                  dispatch_semaphore_signal(semaphore);
                                                              }
                                                              failure:^(AFHTTPRequestOperation *operation, NSError *error) {
                                                                  dispatch_semaphore_signal(semaphore);
                                                              }];
reqOp.failureCallbackQueue = queue;
reqOp.successCallbackQueue = queue;
[self enqueueHTTPRequestOperation:reqOp];
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_release(semaphore);
return result;

Solution 3:

I would suggest that you don't make a synchronous method with AFNetworking (or blocks in general). A good approach is that you make another method and use the json data from the success block as an argument.

- (void)methodUsingJsonFromSuccessBlock:(id)json {
    // use the json
    NSLog(@"json from the block : %@", json); 
}

- (void)someFunction {
    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request
        success:^(NSURLRequest *request, NSHTTPURLResponse *response, id json){
            // use the json not as return data, but pass it along to another method as an argument
            [self methodUsingJsonFromSuccessBlock:json];
        }
        failure:nil];

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    [queue addOperation: operation];
}