The UIKit framework provides the required infrastructure for your iOS apps. It provides the core objects that you need to build apps for iOS and tvOS. You use these objects to display your content onscreen, to interact with that content, and to manage interactions with the system.
If you looked at our example, and open the ViewController.swift file.
//
// ViewController.swift
// FirstApp
//
import UIKit
class ViewController: UIViewController {
@IBAction func changeBackground(_ sender: Any) {
view.backgroundColor = UIColor.lightGray
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
We have added one behavior with one line of code to change the background color when a button is clicked.
@IBAction func changeBackground(_ sender: Any) {
view.backgroundColor = UIColor.lightGray
}
This line of code links our Swift file to that UIKit framework and will allow us access to everything inside it.
import UIKit at the top of the swift file mostly.