领先的安全区域空间，而不是说Xcode 9中的顶部边距？
答
安全区域
苹果说是the portion of your view that is unobscured by bars and other content。来源：Apple - safeAreaLayoutGuide
我的解释：
It is the guide for iPhone X for you to avoid the top notch and the bottom part for the swipe gesture that replaced the home button
这里是一个清晰的视觉图像：