NSView不在Xcode 7的操场上显示

Question

尝试使用游乐场在Xcode中显示NSView，我是否还需要做其他任何事情才能显示视图？

使用Xcode 7.3 OSX 10.11.3

一些代码：

import Cocoa
import XCPlayground

class MyNSView: NSView {
    override func drawRect(dirtyRect: NSRect) {
        let blue = NSColor.blueColor()

        blue.setFill()
        //self.bounds
        NSRectFill(self.bounds)
    }
}

let vc = MyNSView(frame: NSRect(x: 0, y: 0, width: 200, height: 200))
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true
XCPlaygroundPage.currentPage.liveView = vc