[iphone] What's a simple way to get a text input popup dialog box on an iPhone

Since IOS 9.0 use UIAlertController:

UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"My Alert"
                                                           message:@"This is an alert."
                                                          preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
                                                  handler:^(UIAlertAction * action) {
                    //use alert.textFields[0].text
                                                       }];
UIAlertAction* cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDefault
                                                      handler:^(UIAlertAction * action) {
                                                          //cancel action
                                                      }];
[alert addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
    // A block for configuring the text field prior to displaying the alert
}];
[alert addAction:defaultAction];
[alert addAction:cancelAction];
[self presentViewController:alert animated:YES completion:nil];