Calculator UI

calculator.swift

import UIKit
import PlaygroundSupport

extension UIView {
    static func roundedView(x: Int, y: Int) -> UIView {
        let customView = UIView()
        customView.frame = CGRect(
            x: x, y: y,
            width: 60, height: 60)
        customView.backgroundColor = .green
        customView.layer.cornerRadius = customView.frame.width/2
        
        return customView
    }
}

class MyViewController : UIViewController {
    override func loadView() {
        
        let view = UIView()
        view.backgroundColor = .white
        view.translatesAutoresizingMaskIntoConstraints = false
        self.view = view
    }
    
    override func viewDidLoad() {
        let roundedView = UIView.roundedView(x: 0, y: 20)
        roundedView.translatesAutoresizingMaskIntoConstraints = false

        self.view.addSubview(roundedView)
        
        let views = ["roundedView" : roundedView]
        let formatString = "|-50-[roundedView(>=30)]-|"
        
        let constraints = NSLayoutConstraint.constraints(
            withVisualFormat: formatString,
            metrics: nil,
            views: views)
        
        NSLayoutConstraint.activate(constraints)
    }
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()