如何在Go中解组xml枚举属性？

Question

I want to parse an xml attribute as an iota enum type (int) in go.

Below you can see what I tried but this does not work because the address of enum variables can't be taken.

type EnumType int
const (
    EnumUnknown EnumType = iota
    EnumFoo
    EnumBar
)

func (E *EnumType) UnmarshalXMLAttr(attr xml.Attr) error {
    switch attr.Value {
    case "foo":
        E = &EnumFoo
    case "bar":
        E = &EnumBar
    default:
        E = &EnumUnknown
    }
    return nil
}


// Example of how the unmarshal could be called:
type Tag struct {
    Attribute EnumType `xml:"attribute,attr"`
}

func main() {
    tag := &Tag{}
    xml.Unmarshal([]byte("<tag attribute=\"foo\"/>"), tag)
}

Any other way to make UnmarshalXMLAttr work with int types?

Update: I know I can solve this by adding the UnmarshalXML method to Tag but I want to avoid this if possible because I have a lot of different tags with a lot of different attributes but only a few custom typed attributes. So implementing UnmarshalXML methods for each tag would not be preferred.

Answer 1

I solved the problem by wrapping the int in a struct.

type EnumType int
const (
    EnumUnknown EnumType = iota
    EnumFoo
    EnumBar
)
type EnumContainer struct {
    Value EnumType
}

func (E *EnumContainer) UnmarshalXMLAttr(attr xml.Attr) error {
    switch attr.Value {
    case "foo":
        E.Value = EnumFoo
    case "bar":
        E.Value = EnumBar
    default:
        E.Value = EnumUnknown
    }
    return nil
}


// Example of how the unmarshal could be called:
type Tag struct {
    Attribute EnumContainer `xml:"attribute,attr"`
}

func main() {
    tag := &Tag{}
    xml.Unmarshal([]byte("<tag attribute=\"foo\"/>"), tag)

Is there a "more elegant" way or should I be happy with what I now have?