JSON parser returns Null

Question

I am trying to learn how to parse JSON data so I can handle big databases. I wrote code to login into a website.

I have following JSON data from a successful login request:

JSON string : correct username and password [{"user_id":"7","first_name":"dada","last_name":"Kara","e_mail":"yaka@gmail","fullname":"Dada Kara","forum_username":"ycan"}]

and i use following code to parse but it doesnt parse it

-(IBAction)loginButton:(id)sender{

    NSString *username = usernameTextfield.text; 
    NSString *password = passwordTextfield.text;

    NSMutableURLRequest *request =[NSMutableURLRequest requestWithURL:[NSURL URLWithString:kPostUrl]];
    [request setHTTPMethod:@"POST"];

    NSString *post =[[NSString alloc] initWithFormat:@"e_mail=%@&password=%@", username, password];
    [request setHTTPBody:[post dataUsingEncoding:NSASCIIStringEncoding]];

    NSURLResponse *response;
    NSError *err;

    NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
    //NSString *responseStr = [NSString stringWithUTF8String:[responseData bytes]];
    //NSLog(@"Response : %@", responseStr);

    NSString *json_string = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
    NSLog(@"JSON string : %@", json_string);

    SBJsonParser *parser = [[SBJsonParser alloc] init];
    NSDictionary *responseObj = [parser objectWithString:json_string error:nil];
    NSArray *name = [responseObj objectForKey:@"first_name"];

    NSLog(@"Name : %@", name);
}

The result from my NSLog for name is NULL

Where is the problem and how can I parse such a data so when it comes to lots of rows I can save it to the local FMDB database on iphone

------------------------------EDIT---------------------------------------------------------------

Actual problem was response JSON string from server included echo beginning of the string,json parser only parses between double quotes "", so all i just needed to trim echo from string and parse new string.

and bingo!

//trim in coming echo
    NSString *newString1 = [json_string stringByReplacingOccurrencesOfString:@"correct username and password\n" withString:@""];



    SBJsonParser *parser = [[SBJsonParser alloc] init];

    NSArray *responseObj = [parser objectWithString:newString1 error:nil];

    NSDictionary *dataDict = [responseObj objectAtIndex:0];

    NSString *userID = [dataDict objectForKey:@"user_id"];

    NSLog(@"user_id: %@", userID);

output : user_id : 7

The JSON string is an array that contains dictionary, so first extract the dictionary and then parse it. — MByD
– MByD, Commented May 14, 2012 at 7:00
i guess below answer is the one you have mentioned but i still get NULL — SpaceDust__
– SpaceDust__, Commented May 16, 2012 at 3:39

Mangesh · Accepted Answer · 2012-05-16 07:01:53Z

2

 SBJsonParser *parser = [[SBJsonParser alloc] init];

 NSArray *responseObj = [parser objectWithString:json_string error:nil];

NSDictionary *dataDict = [responseObj objectAtIndex:0];

NSString *name = [dataDict objectForKey:@"first_name"];

Did you print recieve data ? is it showing recieve data from server ? If yes then try with different encoding.

edited May 16, 2012 at 7:01

answered May 14, 2012 at 7:56

Mangesh

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5 Comments

SpaceDust__ Over a year ago

yes NSLog(@"JSON string : %@", json_string); prints

JSON string : correct username and password [{"user_id":"7","first_name":"dada","last_name":"Kara","e_mail":"yaka@gmail","fullname":"Dada Kara","forum_username":"ycan"}]

what do u mean by different encoding?

Mangesh Over a year ago

NSString *json_string = [[NSString alloc] initWithData:responseData encoding:Some other encoding]; like NSASCIIStringEncoding & other

SpaceDust__ Over a year ago

problem is my json string begins with correct username and password while a json parser only parses between double quotes "" i need to find a way that parser starts after string correct user name and password

Mangesh Over a year ago

You can create your own string with the Help of Nsstring append format and Then send it to Parser.

Vidhi Over a year ago

Thank you so much. It worked like a charm. I was finding solution for this problem from hours. Thank you again :)

Rexeisen · Accepted Answer · 2012-05-14 19:38:52Z

0

You can use a tool like Objectify ($15 US) or JSON Accelerator ($0.99 US) in the Mac App store to automatically generate data models for you that would make the model as simple as doing object.firstName.

answered May 14, 2012 at 19:38

Rexeisen

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