golang-对嵌入式结构的反思

Question

Given a struct like so:

type B struct {
    X string
    Y string
}

type D struct {
    B
    Z string
}

I want to reflect on D and get to the fields X, Y, Z.

Intuitively, before attempting the solution, I was assuming I would be able to traverse the struct D and get all fields using reflection (X, Y, Z) and won't have to deal with B.

But as you can see, I only see the embedded struct B using reflection and not its fields.

http://play.golang.org/p/qZQD5GdTA8

Is there a way I can make B fully transparent when reflecting on D?

Why do I want this?

Imaging a common struct (B in the example here), that is used in multiple other structs by using embedding. Using reflection, the attempt is to copy D into another similar struct in a different package. The destination struct for copying will have all attributes flatly laid out (no embedding there). So there is a mismatch from the source to the destination (embedding vs no embedding) but all the attributes flatly laid out are the same. I don't want to create custom solutions for each struct.

Answer 1

The 'transparency' you expected is just syntactic sugar and has nothing to do with the data representation. If you want to have a function that flattens your data structure, you would have to write it by yourself.

For example (On play):

func DeepFields(iface interface{}) []reflect.Value {
    fields := make([]reflect.Value, 0)
    ifv := reflect.ValueOf(iface)
    ift := reflect.TypeOf(iface)

    for i := 0; i < ift.NumField(); i++ {
        v := ifv.Field(i)

        switch v.Kind() {
        case reflect.Struct:
            fields = append(fields, DeepFields(v.Interface())...)
        default:
            fields = append(fields, v)
        }
    }

    return fields
}