AFNetworking multipart upload

+ (NSDictionary*)parametersOfUser:(User*)user{
    if (user) {
        NSMutableDictionary *returnDict = [NSMutableDictionary dictionaryWithCapacity:0];
        if (user.userId && [user.userId length]) {
            [returnDict setObject:[user.userId urlEncoded] forKey:@"userId"];
        }
        
        if (user.userName && [user.userName length]) {
            [returnDict setObject:[user.userName urlEncoded] forKey:@"userName"];
        }
        if (user.phone && [user.phone length]) {
            [returnDict setObject:[user.phone urlEncoded] forKey:@"phone"];
        }
        if (user.email && [user.email length]) {
            [returnDict setObject:[user.email urlEncoded] forKey:@"email"];
        }
        
        [returnDict setObject:[user.deviceId urlEncoded] forKey:@"deviceId"];
        [returnDict setObject:[user.deviceType urlEncoded] forKey:@"deviceType"];
        [returnDict setObject:[user.osName urlEncoded] forKey:@"osName"];
        [returnDict setObject:[user.osVersion urlEncoded] forKey:@"osVersion"];
        
        if (user.pinCodeHash && [user.pinCodeHash length]) {
            [returnDict setObject:[user.pinCodeHash urlEncoded] forKey:@"pinCodeHash"];
        }
        if (user.publicKey && [user.publicKey length]) {
            [returnDict setObject:[user.publicKey urlEncoded] forKey:@"publicKey"];
        }
        
        return returnDict;
    }return nil;
}

NSMutableURLRequest *afRequest = [client multipartFormRequestWithMethod:@"POST"
                                                                           path:path
                                                                     parameters:[User parametersOfUser:user]
                                                      constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
                                                          /**
                                                           *@discussion If we use multipart, we should only have two parts, one for picture (probably type is image/png) and one for other parameters (type is x-www-form-urlencoded)
                                                           */
                                                          //header
                                                          /*
                                                           NSString *bodyString = [User postBodyStringWithUser:user withPostType:PostTypeMultiPart];
                                                           
                                                           NSMutableDictionary *headers = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                                           @"application/x-www-form-urlencoded; charset=UTF-8",@"Content-Type",
                                                           [NSString stringWithFormat:@"form-data; name=\"%@\"", @"usr_info"],@"Content-Disposition"
                                                           , nil];
                                                           [formData appendPartWithHeaders:headers body:[bodyString dataUsingEncoding:NSUTF8StringEncoding]];
                                                           */
                                                          //picture part
                                                          if (user.picture2) {
                                                              NSData *data = UIImagePNGRepresentation(user.picture2);
                                                              //NSLog(@"=====data length is %i",[data length]);
                                                              [formData appendPartWithFileData:data
                                                                                          name:@"picture2"
                                                                                      fileName:nil
                                                                                      mimeType:@"image/*"];
                                                          }
                                                      }];