NSError *error = NULL;
NSData* data = [yourJsonString dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:data
options:kNilOptions
error:&error];
NSArray *resultArray = [json objectForKey:@"ns"];//resultArray contains array type objects...
I think it will be helpful to you.