如何从嵌入式结构的方法反映包含结构的字段？

Question

The output of this program is map[], but I want map[Id:true name:true]

I'm trying to dry up some of my SQL CRUD code and thought it would be nice to embed a persistence struct that handles reading and writing to the database. In the example below, the persistence struct would be Inner and my model would be Outer. Thanks!

http://play.golang.org/p/fsPqJ-6aLI
package main

import (
    "fmt"
    "reflect"
)

type Inner struct {
}

type Outer struct {
    Inner
    Id   int
    name string
}

func (i *Inner) Fields() map[string]bool {
    typ := reflect.TypeOf(*i)
    attrs := make(map[string]bool)

    if typ.Kind() != reflect.Struct {
        fmt.Printf("%v type can't have attributes inspected
", typ.Kind())
        return attrs
    }

    // loop through the struct's fields and set the map
    for i := 0; i < typ.NumField(); i++ {
        p := typ.Field(i)
        if !p.Anonymous {
            v := reflect.ValueOf(p.Type)
            v = v.Elem()
            attrs[p.Name] = v.CanSet()

        }
    }

    return attrs
}

func main() {
    val := Outer{}
    fmt.Println(val.Fields()) // prints map[], but I want map[Id:true name:true]
}

Answer 1

You can't. You're specifically calling a method on Inner, which has no knowledge of where it's embedded. Embedding isn't inheritance, it's simple automatic delegation.

You probably want to look in the direction of wrapping these in a common persistence interface, or even a generic function that can handle persisting your data types.

---

Now, if you really want to try this, you can get access to the outer struct through the pointer address, but you will need to know that outer type you want to access, which means that you can't get it via reflection.

outer := (*Outer)(unsafe.Pointer(i))
typ := reflect.TypeOf(*outer)