"Use of unresolved indentifier 'self'" with button.addTarget - ios

Question

I am a beginner to Swift. I have created a very simple button component, but when I try to add a function that is tied to the button click, I get the error: "Use of unresolved identifier 'self.'" Here is my code:
import UIKit
import PlaygroundSupport
let containerView = UIView (frame: CGRect(x: 0, y: 0, width: 600, height: 600))
containerView.backgroundColor = UIColor.blue
let button = UIButton (frame: CGRect(x: 100, y: 100, width: 200, height: 200))
button.backgroundColor = UIColor.yellow
button.setTitle("Test Button", for: .normal)
button.setTitleColor(.red, for: .normal)
button.layer.cornerRadius = 10
func ButtonClicked(_ sender: UIButton) {
print()
}
button.addTarget(self, action: #selector(ButtonClicked), for: .touchUpInside)
containerView.addSubview(button)
PlaygroundPage.current.liveView = containerView
Any help would be appreciated greatly, thanks!

Answer 1

As mentioned in the comments, there is no self to reference in your code as you're not working within a class or struct. The first thing you'll want to do is to wrap this stuff up into a class, and reorganize it a bit. I'd suggest going back to Xcode and doing the following:
File > New > Playground…
Select iOS > Single View
Save this new Playground somewhere.
Now, you should have a simple Playground created from a template. Here, you'll be able to see how a new class called MyViewController that inherits from UIViewController is created. Within that, you'll find a function called loadView(). Then, outside the class, you'll see where this new view controller is created and placed into the PlaygroundPage's current liveView.
Ideally, you should be able to click the Play button at the bottom of the code view, and if the Assistant editor is open, you'll see a simple view with a "Hello World!" label in the center of the view. (The assistant button is the one with the two interlocking circles.)
Assuming that runs and works for you, then I'd suggest you start adding your code back in and try to follow the patterns setup in the template. Place your code that sets up the view in the loadView() function, and move the ButtonClicked() function outside of that, but still within the class.
With a few modifications, you should be able to get up and running, and start playing around with Swift. As an example, here's a working version of your Playground code:
//: A UIKit based Playground for presenting user interface
import UIKit
import PlaygroundSupport
class MyViewController : UIViewController {
override func loadView() {
let containerView = UIView (frame: CGRect(x: 0, y: 0, width: 600, height: 600))
containerView.backgroundColor = UIColor.blue
let button = UIButton (frame: CGRect(x: 100, y: 100, width: 200, height: 200))
button.backgroundColor = UIColor.yellow
button.setTitle("Test Button", for: .normal)
button.setTitleColor(.red, for: .normal)
button.layer.cornerRadius = 10
button.addTarget(self, action: #selector(ButtonClicked), for: .touchUpInside)
containerView.addSubview(button)
self.view = containerView
}
#objc func ButtonClicked(_ sender: UIButton) {
print("ButtonClicked")
}
}
PlaygroundPage.current.liveView = MyViewController()
Have fun, spend some quality time with the Swift Programming Guide, and things'll start to make sense soon enough.