将[] string转换为[] interface {}

Question

I just want to write some code like this:

func (w Writer) WriteVString(strs []string) (int, error) {
    return writeV(func(index int, str interface{}) (int, error) {
        return w.WriteString(str.(string))
    }, strs) // it doesn't work
}

func (w Writer) WriteV(bs [][]byte) (int, error) {
    return writeV(func(index int, b interface{}) (int, error) {
        return w.Write(b.([]byte))
    }, []interface{}{bs...}) // it also can't be compiled
}
type writeFunc func(int, interface{}) (int, error)

func writeV(fn writeFunc, slice []interface{}) (n int, err error) {
    var m int
    for index, s := range slice {
        if m, err = fn(index, s); err != nil {
            break
        }
        n += m
    )
    return
}

I thought interface{} can represent any type, so []interface can also represent any []type before, now I know I'm wrong, []type is a whole type, can't be considered as []interface{}.

So, can anyone help me how to make this code work, or any other solution?

PS: I know that []byte or string can be converted to one another, but it's not actually my intention, may be there is another type rather than []byte and string.

Answer 1

now I know I'm wrong, []type is a whole type, can't be considered as []interface{}.

Yes, and that is because interface{} is its own type (and not an "alias" for any other type).
As I mention in "what is the meaning of interface{} in golang?" (if v is a interface{} variable):

Beginner gophers are led to believe that “v is of any type”, but that is wrong.
v is not of any type; it is of interface{} type.

The FAQ mentions

they do not have the same representation in memory.

It is necessary to copy the elements individually to the destination slice.
This example converts a slice of int to a slice of interface{}:

t := []int{1, 2, 3, 4}
s := make([]interface{}, len(t))
for i, v := range t {
    s[i] = v
}