Question

I am new in iOS. I created a JSON NSDictionary like this:

NSArray *keys = [NSArray arrayWithObjects:@"User", @"Password", nil];
NSArray *objects = [NSArray arrayWithObjects:@"Ali", @"2020", nil];
NSDictionary *jsonDictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys];

And then I could convert it to NSString via two mechanisms:

1)

NSError *error; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonDictionary options:0 error:&error];

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

2)

NSString *jsonString = [jsonDictionary JSONRepresentation];

In the second way I get this warning :

Instance method '-JSONRepresentation' not found (return type defaults to 'id')

But when I run the project, both of the mechanisms works fine:

NSLog(@"Val of json parse obj is %@",jsonString); 

Do you know how can I remove the warning in the second way?

My main goal is POST this json String to an external database using RESTful Web Service.
Basically which way is better considering my main goal?

Answer 1

You should use NSJSONSerialization as it is faster and comes directly with iOS SDK as long as your “target audience” is iOS5+

To POST the data to your web service you need the create a request along these lines…

NSDictionary * postDictionary = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"value1", @"value2", nil]
                                                                  forKeys:[NSArray arrayWithObjects:@"key1", @"key2", nil]];

NSError * error = nil;
NSData * jsonData = [NSJSONSerialization dataWithJSONObject:postDictionary options:NSJSONReadingMutableContainers error:&error];

NSMutableURLRequest * urlRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"your_webservice_post_url"]];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[urlRequest setHTTPMethod:@"POST"];
[urlRequest setHTTPBody:jsonData];

NSURLConnection * myConnection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self startImmediately:YES];

Please read up on NSURLConnectionDelegate protocol.