UIButton，UIAlertView设置动作

Question

I have a simple question, please help me as I really stuck. What I need is to switch to another ViewController after login button is pressed if login and password are not empty

I have a simple login interface with username, password and login button. UIAlertView is shown when password or login is empty, here's code:

.m file

- (IBAction)login:(id)sender {
    if (userName.text.length == 0 || password.text.length == 0){
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Complete All Fields" message:@"You must complete all fields to login!" delegate:self cancelButtonTitle:@"Good" otherButtonTitles:nil, nil];
        [alert show]; 
    }
}

How to add action for the button to switch to other UIController? This one is crushing all the time [self presentModalViewController: anotherUIViewController animated YES]; Here's also notification -"Application tried to present a nil modal view controller on target ."

Answer 1

Only keep one of the lines as explained below depending on if you are using xibs or storyboards.

- (IBAction)login:(id)sender {
    if (userName.text.length == 0 || password.text.length == 0){
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Complete All Fields" message:@"You must complete all fields to login!" delegate:self cancelButtonTitle:@"Good" otherButtonTitles:nil, nil];
        [alert show];
    }else{
        //if you are using xibs use this line
        UIViewController *anotherUIViewController = [[UIViewController alloc] initWithNibName:@"anotherUIViewController" bundle:[NSBundle mainBundle]];
        //
        //if you are using storyboards use this line
        UIViewController *anotherUIViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"someIdentifierForThisController"];
        //
        //then simply present the view controller
        [self presentViewController:anotherUIViewController animated:YES completion:nil];
    }
}