example1.swift

import UIKit
import XCPlayground

class ViewController: UIViewController {
    func action() { print("Bing!") }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .whiteColor()
        
        let mySwitch : UISwitch = {
            view.addSubview($0)
            CenterViewInSuperview($0,
                horizontal: true, vertical: true)
            $0.addTarget(self, action: "action",
                forControlEvents: .TouchUpInside)
            return $0
        }(UISwitch())
        
        let _ : UILabel = {
            view.addSubview($0)
            CenterViewInSuperview($0,
                horizontal: true, vertical: false)
            $0.text = "Toggle me"
            $0.font = UIFont.boldSystemFontOfSize(36)
            ConstrainViews("V:[view1]-30-[view2]",
                views: $0, mySwitch)
            return $0
        }(UILabel())
    }
}

ViewController()

XCPlaygroundPage.currentPage.liveView = ViewController()
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

unfortunately CenterViewInSuperview is missing -> Use of unresolved identifier "CenterViewInSuperview"

you can use this tiny library for CenterViewInSuperview:
https://gist.github.com/erica/a0f4ee23e9ee5dc1b489

然而，用这种方式在XCode10.2.1上无法使用代码提示。