Use of unresolved identifier 'XCPlaygroundPage'

XCPlaygroundPage.playground

//: Playground - noun: a place where people can play

import UIKit
import XCPlayground

class VC: UIViewController {
    let newView = UIView()
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        newView.frame = view.bounds
        newView.backgroundColor = .redColor()
        UIView.transitionFromView(view,
            toView: newView,
            duration: 3.0,
            options: [.TransitionCurlUp],
            completion: nil)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .greenColor()
    }
}

let vc = VC()

let currentPage = XCPlaygroundPage.currentPage
currentPage.needsIndefiniteExecution = true
currentPage.liveView = vc