How to subclass different View Controllers in Swift

Question

How do I subclass different view controllers? This is what I've been trying to use:

class secondViewController: UIViewController {

This returns the error "Use of undeclared type UIViewController." What am I doing wrong?

I have started this class in a new .swift file, is that somehow contributing to the problem?

I would greatly appreciate a brief summary of what to do and a link to a GitHub repository that demonstrates how to do this.

Answer 1

如果要对UIKit类进行子类化（或使用），则需要在文件顶部import UIKit 。

Answer 2

The problem I had was that I did not know how to connect my view controller to the class using the navigation panel, and I was importing foundation instead of importing UIKit. See this for more details:

IBOutlets on second view controller help on swift