Swiftでマウスをクリックするコードを書きたい

Question

Xcodeで所謂マウスクリックツールを作りたく思い、まずこちらのサイトを参考に(というかコピペして)実行するとマウスをクリックするというplaygroundを作ってみたのですが、うまくいきませんでした。どこを直せばいいでしょうか

import Cocoa
import AppKit

func leftClickDown(position: CGPoint) {
    let source = CGEventSource(stateID: CGEventSourceStateID.hidSystemState)
    let event = CGEvent(mouseEventSource: source, mouseType: CGEventType.leftMouseDown,
                        mouseCursorPosition: position, mouseButton: CGMouseButton.left)
    event?.post(tap: CGEventTapLocation.cghidEventTap)
}

func leftClickUp(position: CGPoint) {
    let source = CGEventSource(stateID: CGEventSourceStateID.hidSystemState)
    let event = CGEvent(mouseEventSource: source, mouseType: CGEventType.leftMouseUp,
                        mouseCursorPosition: position, mouseButton: CGMouseButton.left)
    event?.post(tap: CGEventTapLocation.cghidEventTap)
}

func leftDragged(to: CGPoint, from: CGPoint) {
    leftClickDown(position: from)
    let source = CGEventSource(stateID: CGEventSourceStateID.hidSystemState)
    let event = CGEvent(mouseEventSource: source, mouseType: CGEventType.leftMouseDragged,
                        mouseCursorPosition: to, mouseButton: CGMouseButton.left)
    event?.post(tap: CGEventTapLocation.cghidEventTap)
    leftClickUp(position: to)
}
// 現在のマウス座標にてクリックを行う
var location = NSEvent.mouseLocation
for screen in NSScreen.screens {
    if screen.frame.contains(location) {
        location = CGPoint(x: location.x, y: NSHeight(screen.frame) - location.y)
        break
    }
}
leftClickDown(position: location)
leftClickUp(position: location)

エラーメッセージ

error: Couldn't lookup symbols:
  _CGEventCreateMouseEvent
  _CGEventCreateMouseEvent