Xcode error message: 'No visible @interface for 'UIAlertAction' declares the selector....'

Question

So, I am trying to make an app with a passcode lock on it for my iPhone (iOS 12) on Xcode 10. I am in the ViewController.m file and am trying to run the code:

    NSString *passwordString = [NSString stringWithFormat:@"1234"]; //CHANGE PASSWORD HERE
    if ([passwordField.text isEqualToString:passwordString]) {
        UIAlertAction *alert = [[UIAlertAction alloc] initWithTitles:@"Success" message:@"Success" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

But every time seemingly no matter what I try (as suggested by other posts) I get the same red error message pop up:

No visible @interface for 'UIAlertAction' declares the selector 'initWithTitle:message:delegate:cancelButtonTitle:otherButtonTlttes:'

I've tried turning ARC off, but it doesn't seem to be giving me the option to? I've also tried importing the file in the AppDelegate.

The problem may be that some of the tutorials I have watched are outdated in older versions of Xcode.