Generate JSON from an NSDictionary.

nsdictionarytojson.m

NSError *error; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionaryOrArrayToOutput options:NSJSONWritingPrettyPrinted error:&error];

if (!jsonData) {
    NSLog(@"Got an error: %@", error);
} else {
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}