如何在Swift中以编程方式访问系统颜色？

Question

I'm trying to programmatically set the background color of an UIButton to the color UIColor.systemBlue , which I assume should be accessible according to the docs of UIColor and the color guidelines . However, I can only access the regular colors such as .blue and .red . In the interface builder I can select systemBlue but not programmatically.

I'm using Xcode 10.3 and building for iOS 12.4.

EDIT : I've seen the question iOS 11.x system colors , but it doesn't make sense. In the color guidelines it's clearly stated that the system color values shouldn't be hard-coded, but to use the API instead. And in the UIColor docs the system colors seem to be accessible as public class vars of UIColor.

Answer 1

这些系统颜色仅在使用iOS 13 SDK时可用，这意味着您必须使用Xcode 11，而不是Xcode 10.3。