IOS - How can I inspect the JSON NSData the SBJson creates?

Question

I am attempting to POST some simple JSON to a RESTful service. I want to form a json string that takes the following form:

{username:"someuser",password:"somepassword"}

My POST keeps failing at the server complaining that POSTed values do not exist. However the same service works fine if I create a JS test implementation. So I'm pretty sure its my SBJson client implementation that is the problem.

NSDictionary *userDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                          userName,@"username",
                          password, @"password",
                          nil];
SBJsonWriter *writer = [[SBJsonWriter alloc]init];
NSData *jsonData = [writer dataWithObject:userDict];    

jsonData appears to have size but it attempt to serialize it with SBJson its fails and I get nil.

NSString *test = [writer stringWithObject:jsonData]; // returns nil

I am trying to post the above in a NSMutableURLRequest. Here's my implementation if it helps give context:

-(void)registerUserName:(NSString *)userName andPassword:(NSString *)password{
responseData = nil;
responseData = [NSMutableData data];
NSDictionary *userDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                          userName,@"username",
                          password, @"password",
                          nil];
SBJsonWriter *writer = [[SBJsonWriter alloc]init];
NSData *jsonData = [writer dataWithObject:userDict];
NSString *test = [writer stringWithObject:jsonData]; //always nil
NSURL *url = [[NSURL alloc] initWithString:@"http://localhost/~user/app_web/index.php/user/create"];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"POST"];
[request addValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request addValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request addValue:@"form-data" forHTTPHeaderField:@"Content-Disposition"];
[request setHTTPBody:jsonData];
[[UIApplication sharedApplication]setNetworkActivityIndicatorVisible:YES ];
currentRequestType = REGISTER_USER;
NSURLConnection *connection =[[NSURLConnection alloc]initWithRequest:request delegate:self]; 

Thanks!

update

Using the suggestions below I am now doing this:

NSDictionary *userDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                              userName,@"username",
                              password, @"password",
                              nil];



     NSString *jsonString = [userDict JSONRepresentation];
    NSData *jsonData = [jsonString dataUsingEncoding];
    [request setHTTPBody:jsonData];
        [[UIApplication sharedApplication]setNetworkActivityIndicatorVisible:YES ];
        currentRequestType = REGISTER_USER;
        NSURLConnection *connection =[[NSURLConnection alloc]initWithRequest:request delegate:self];

Unfortunately my posted values are still not found at the server. I think something must be wrong with my NSMutableURLRequest..

I am using CodeIgniter on the backend. The action looks like this:

public function create(){
    if($this->input->post('username') && $this->input->post('password')){
        $username = $this->input->post('username');
        $password = $this->input->post('password');
        $this->load->model('User_model','users');
        $status = $this->users->add_user($username,$password);
        if($status){
            echo json_encode(array('success'=>true));
        } else{
            echo json_encode(array('success'=>false));
        }
    }
     echo json_encode(array('success'=>false)); // when posting I arrive here
}

Answer 1

To serialize the dictionary userDict call the following method.

NSString* jsonString = [userDict JSONRepresentation];

If you want the NSData representation you can use the following method

NSData* jsonData = [jsonString dataUsingEncoding:NSUTF8Encoding];

Answer 2

try this:

NSDictionary *userDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                      userName,@"username",
                      password, @"password",
                      nil];
SBJsonWriter *writer = [[SBJsonWriter alloc]init];
NSString *test = [writer stringWithObject:userDict]; 

don't forget to release them