英文:
Workaround for lack of support for array constants?
问题
Go语言没有数组常量。
我的应用程序接收包含多种类型的数字代码的消息，我需要将其显示为短语。
如果存在数组常量，我可以这样做：
func foo() {...fmt.Println(facename[f])...}const facename [...]string = "top", "bottom", "left", "right", "front", "back"
但是当然没有办法这样做。我能想到的第一种解决方法，也许是一种合理高效的方法，是使用switch语句：
func foo() {...name := "unknown"switch f {case 0:name = "top"case 1:name = "bottom"case 2:name = "left"case 3:name = "right"case 4:name = "front"case 5:name = "back"}fmt.Println(name)...}
如果值的数量达到二十个或更多，上述方法会变得相当繁琐。
似乎最简洁的方法是这样的：
func foo() {...fmt.Println(strings.Split(facenames, ",")[f])...}const facenames = "top,bottom,left,right,front,back"
当然，我还需要检查索引是否在范围内。虽然效率目前不是问题，但我不希望过多地使用strings.Split()。
是否有其他既符合惯用方式又简洁高效的方法？
英文:
Go doesn't have array constants.
My application receives messages containing several types of numeric codes which I need to display as phrases.
If array contants existed I could do something like:
<!-- language: go -->
func foo() {...fmt.Println(facename[f])...}const facename [...]string = "top", "bottom", "left", "right", "front", "back"
But of course there's no way to do this. The first way around this that occurs to me, and maybe a reasonable efficient one is to use a switch
<!-- language: go -->
func foo() {...name := "unknown"switch f {case 0:name = "top"case 1:name = "bottom"case 2:name = "left"case 3:name = "right"case 4:name = "front"case 5:name = "back"}fmt.Println(name)...}
The above is rather tedious if the number of values gets to be twenty or more.
It seems the most concise way is something like
<!-- language: go -->
func foo() {...fmt.Println(strings.Split(facenames,",")[f])...}const facenames = "top,bottom,left,right,front,back"
I will also have to check that the index is in range of course.
Although efficiency isn't a concern at the moment, it bugs me that
I'm using strings.Split() more than I want to.
Is there another way that is either idiomatic or both concise and efficient?
答案1
得分: 2
惯用的方法是使用包级别的变量：
var facename = []string{"top", "bottom", "left", "right", "front", "back"}func foo() {// ...fmt.Println(facename[f])// ...}
在这种情况下，使用切片而不是数组也是惯用的做法。
英文:
The idiomatic approach is to use a package level variable:
var facename = []string{"top", "bottom", "left", "right", "front", "back"}func foo() {// ...fmt.Println(facename[f])// ...}
It's also idiomatic to use a slice instead of an array in this situation.
答案2
得分: 0
可能并不是一个很好的匹配，但是你的用例似乎基本上是一个具有字符串等效项的枚举。对于这种情况，我通常会采取以下方式：
type Face uint8const (FaceTop Face = iotaFaceBottomFaceLeftFaceRightFaceFrontFaceBack)func (f Face) String() string {switch f {case FaceTop: return "top"case FaceBottom: return "bottom"case FaceLeft: return "left"case FaceRight: return "right"case FaceFront: return "front"case FaceBack: return "back"default: return "" // 或者添加一个错误返回，或者在枚举中添加一个零值}}func ParseFace(in string) (Face, error) {switch in {case "top": return FaceTop, nilcase "bottom": return FaceBottom, nilcase "left": return FaceLeft, nilcase "right": return FaceRight, nilcase "front": return FaceFront, nilcase "back": return FaceBack, nildefault: return "", errors.New("无效的面名称" + in)}}
以上是一个示例代码，用于将枚举类型与字符串等效项进行转换。
英文:
It may not be a good fit, but it appears your use case is basically an enum with string equivalents. For this I usually do something along the lines of:
type Face uint8const (FaceTop Face = iotaFaceBottomFaceLeftFaceRightFaceFrontFaceBack)func (f Face) String() string {switch f {case FaceTop: return "top"case FaceBottom: return "bottom"case FaceLeft: return "left"case FaceRight: return "right"case FaceFront: return "front"case FaceBack: return "back"default: return "" // Or add an error return, or add a zero value to the enum}}func ParseFace(in string) (Face,error) {switch in {case "top": return FaceTop,nilcase "bottom": return FaceBottom,nilcase "left": return FaceLeft,nilcase "right": return FaceRight,nilcase "front": return FaceFront,nilcase "back": return FaceBack,nildefault: return "",errors.New("invalid face name"+in)}}
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