How to create a custom UITextField prepackaged with its own formatting behavior?

Question

I am trying to make a reusable textfield that will format its contents to be in a currency format without relying on a containing viewcontroller to implement this behavior for it.

Right now the viewcontroller that the textfield is in is implementing the desired behavior in a TextFieldChange action and it works fine:

class MyViewController: UIViewController {
    @IBOutlet weak var TextField: UITextField!
    ...
    ...
    @IBAction func TextFieldChanged(_ sender: Any) {
        // Format text in text field
    }
}

This works, but that means I'll have to copy and paste this code into every viewcontroller that I want to have this functionality. I would like it so I could just assign the textfield its own class in the inspector so that this behavior will be a part of every textfield I make using this class. How do I do this?