指针，数组和切片的结构值

Question

I want to have a generic way which will always return the struct value no matter if it is provided as pointer, slice or array.

My approach towards this looks:

func main() {
    p := Person{}

    if value(p).Kind() != reflect.Struct {
        fmt.Printf("Error 1")
    }
    if value(&p).Kind() != reflect.Struct {
        fmt.Printf("Error 2")
    }   
    if value([]Person{p}).Kind() != reflect.Struct {
        fmt.Printf("Error 3")
    }
    if value(&[]Person{p}).Kind() != reflect.Struct {
        fmt.Printf("Error 4")
    }
}

func value(m interface{}) reflect.Value {
    v := reflect.ValueOf(m)

    switch v.Kind() {
    case reflect.Ptr:
        v = v.Elem()

        fallthrough
    case reflect.Slice, reflect.Array:
        v = v.Elem()
    }

    return v
}

Go Playground

As you can see the problem lays with in getting the struct out of a slice or array.

How do I need to extend the above function to get the struct value from with in an array or slice?

Update: What I want to do is turn []People into People.

Answer 1

If you just want the type even if the slice is nil, you can use something like this:

func value(m interface{}) reflect.Type {
    t := reflect.Indirect(reflect.ValueOf(m)).Type()
    if t.Kind() == reflect.Slice || t.Kind() == reflect.Array {
        t = t.Elem()
        if t.Kind() == reflect.Ptr {
            t = t.Elem()
        }
        return t

    }
    return t
}

About Type.Elem(), from http://golang.org/pkg/reflect/#Type:

// Elem returns a type's element type.

// It panics if the type's Kind is not Array, Chan, Map, Ptr, or Slice.

//edit updated the function to work on a slice of pointers as well.