swift语言点评十五-$0

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