This question already has an answer here:
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:
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
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
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?
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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.
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 uint8
const (
FaceTop Face = iota
FaceBottom
FaceLeft
FaceRight
FaceFront
FaceBack
)
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,nil
case "bottom": return FaceBottom,nil
case "left": return FaceLeft,nil
case "right": return FaceRight,nil
case "front": return FaceFront,nil
case "back": return FaceBack,nil
default: return "",errors.New("invalid face name"+in)
}
}