MGTwitterEngine check if following a user

I am using MGTwitterEngine SDK in my iOS app. I am trying to check if a user is following another user with this method:

- (NSString *)isUser:(NSString *)username1 receivingUpdatesFor:(NSString *)username2
{
    if (!username1 || !username2) {
        return nil;
    }
    NSMutableDictionary *params = [NSMutableDictionary dictionaryWithCapacity:0];
    [params setObject:username1 forKey:@"user_a"];
    [params setObject:username2 forKey:@"user_b"];

    NSString *path = [NSString stringWithFormat:@"friendships/exists.%@", API_FORMAT];

    return [self _sendRequestWithMethod:nil path:path queryParameters:params body:nil 
                            requestType:MGTwitterUpdatesCheckRequest 
                           responseType:MGTwitterMiscellaneous];
}

this method is always returning a string that is in this format but not the same:

CB4C097E-6740-4536-885E-BAF7D8A981FD

basically it would be better to get a bolean value, I don't have a clue about what I'm going to do with this value.

any ideas?

**EDIT the code that initialized the _engine

        _engine = [[SA_OAuthTwitterEngine alloc] initOAuthWithDelegate: self];
    _engine.consumerKey = kOAuthConsumerKey;
    _engine.consumerSecret = kOAuthConsumerSecret;

Solution

This is an asynchronous request, you have to set your class as delegate of the MGTwitterEngine and get the result in these method, that you must implement in your class:

- (void)statusesReceived:(NSArray *)statuses forRequest:(NSString *)connectionIdentifier;
- (void)directMessagesReceived:(NSArray *)messages forRequest:(NSString *)connectionIdentifier;
- (void)userInfoReceived:(NSArray *)userInfo forRequest:(NSString *)connectionIdentifier;
- (void)miscInfoReceived:(NSArray *)miscInfo forRequest:(NSString *)connectionIdentifier;

As you can read in the MGTwitterEngineDelegate.h:

// These delegate methods are called after all results are parsed from the connection. If 
// the deliveryOption is configured for MGTwitterEngineDeliveryAllResults (the default), a
// collection of all results is also returned.

There you can check the result value.