objective-c - 为什么borderColor要使用CGColor而不能使用UIColor

Question

我在别的地方看到这样一句话
CALayer sits at a lower technical level than UIButton, which means it doesn't understand what a UIColor is. UIButton knows what a UIColor is because they are both at the same technical level, but CALayer is below UIButton, so UIColor is a mystery.

Answer 1

CGColor exists in the lower-level CoreGraphics framework, it is a structure
UIColor exists in the UIKit framework, which is higher than the CoreGraphics framework, and it is a class

CoreGraphics framework can be used across platforms, while UIKit framework is limited to iOS
In order to ensure portability and unity of the framework, they cannot be used interoperably