Swift enum raw value: not working with CGFloat = -1.0

问题:

What does this not work?

enum Aspect : CGFloat {     case Clockwise = 1.0     case Anticlockwise = -1.0 } 

On Anticlockwise line I'm told that 'raw value for enum case must be a literal'

回答1:

That sounds like a bug. However it seems to work if you omit the decimal part:

enum Aspect : CGFloat {     case Clockwise = 1     case Anticlockwise = -1 } 

回答2:

The weird thing is that a float with a minus is not a literal, but an expression. So the error message is correct.

From the Swift programming language:

Unlike with integer literals, negative floating-point numbers are expressed by applying the unary minus operator (-) to a floating-point literal, as in -42.0. The result is an expression, not a floating-point literal.

回答3:

This has been fixed in Swift 1.2 (Xcode 6.3 beta). From the release notes:

Negative floating-point literals are now accepted as raw values in enums.

So your code now compiles and works without problems, and you can now also define non-integral negative enumeration values, which was not possible before:

enum Aspect : CGFloat {     case Clockwise = 1.0     case Anticlockwise = -1.0     case Strange = -1.25 } 

文章来源: Swift enum raw value: not working with CGFloat = -1.0