What is the difference between UIViewController and UIInputViewController ios swift

Question

Here I'am working on CustomKeyboardExtension. In my extensible .swift class file the class definition starts with UIInputViewController

class KeyboardViewController: UIInputViewController {

    @IBOutlet var nextKeyboardButton: UIButton!

    override func updateViewConstraints() {
        super.updateViewConstraints()

        // Add custom view sizing constraints here
    }
}

So what is the difference between UIViewController and UIInputViewController.

Answer 1

UIInputViewController is a subclass of UIViewController. It has all the same functionality as UIViewController but also includes some extra logic. It is specifically designed for creating custom keyboards.

What all features are added into UIInputViewController is best seen in official documentation.