问Xcode PlayGround不显示这些场景的视图

EN

import SpriteKit
import XCPlayground

// lets create a view
let view = SKView(frame: CGRect(x: 0, y: 0, width: 1024, height: 768))

XCPShowView("my first view", view)

let scene = SKScene(size: CGSize(width: 1024, height: 768))
scene.scaleMode = SKSceneScaleMode.AspectFit
view.presentScene(scene)

scene.backgroundColor = SKColor.blackColor()

let blueBox: SKSpriteNode = SKSpriteNode(color: UIColor.blueColor(), size:     CGSizeMake(300, 300))
blueBox.position = CGPointMake(512, 384)
scene.addChild(blueBox)

view.presentScene(scene)