NSString *strURL2 = [NSString stringWithFormat:@"MyURL"];
NSData *dataURL2 = [NSData dataWithContentsOfURL:[NSURL URLWithString:strURL2]];

NSString *strResult2 = [[NSString alloc] initWithData:dataURL2 encoding:NSUTF8StringEncoding];
NSDictionary *json2 = [strResult2 JSONValue];

userExists = [json2 valueForKeyPath:@"userId"];

NSString *strURL2 = [NSString stringWithFormat:@"MyURL"];
NSData *dataURL2 = [NSData dataWithContentsOfURL:[NSURL URLWithString:strURL2]];

NSString *strResult2 = [[NSString alloc] initWithData:dataURL2 encoding:NSUTF8StringEncoding];
NSDictionary *json2 = [strResult2 JSONValue];

[userExists addObject:[[json2 objectForKey:@"userId"] integerValue]]

if([userExists objectAtIndex:i] == [[json2 objectForKey:@"userId"] integerValue]) {
....
}