How to convert JSON serialized data to NSDictionary

I have used this method,

NSDictionary *jsonObject=[NSJSONSerialization 
       JSONObjectWithData:jsonData 
                  options:NSJSONReadingMutableLeaves 
                    error:nil];
NSLog(@"jsonObject is %@",jsonObject);

It's printing "jsonObject is null".
Is there any problem with "error:nil".
I am not using any url or connection methods.
I have a json file and I want to display it in a table.

Please Try the following Code.

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
                                                     options:kNilOptions 
                                                       error:&error];

NSArray* latestLoans = [json objectForKey:@"loans"];

NSLog(@"loans: %@", latestLoans);

Just in case anyone is here to see swift code:

NSData to NSDictionary

let dictionary:NSDictionary = NSKeyedUnarchiver.unarchiveObjectWithData(jsonData)! as NSDictionary

NSData to NSString

let resstr = NSString(data: res, encoding: NSUTF8StringEncoding)

Check your json input, could it be that your root element is neither a dictionary nor an array? The documentation says you have to specify NSJSONReadingAllowFragments as the option in this case.

#import <Foundation/Foundation.h>

int main(int argc, char *argv[]) {
    NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];

    NSData *jsonData = [@"{ \"key1\": \"value1\" }" dataUsingEncoding:NSUTF8StringEncoding];
    NSDictionary *jsonObject=[NSJSONSerialization 
           JSONObjectWithData:jsonData 
                      options:NSJSONReadingMutableLeaves 
                        error:nil];
    NSLog(@"jsonObject is %@",jsonObject);

    [p release];
}

Output:

2012-09-26 16:06:51.610 Untitled[19164:707] jsonObject is {
    key1 = value1;
}