ghetto_unmarshaler.go

package main

import (
	"encoding"
	"encoding/json"
	"fmt"
)

func main() {

	var str string
	if err := unmarshaler(&str); nil != err {
		fmt.Println(err)
		return
	}
	fmt.Printf("str=%s\n", str)

	si := &simple{}
	if err := unmarshaler(si); nil != err {
		fmt.Println(err)
		return
	}
	fmt.Printf("simple=%+v\n", si)

	b := []byte{}
	if err := unmarshaler(&b); nil != err {
		fmt.Println(err)
		return
	}
	fmt.Printf("b=%s\n", b)
}

type simple struct {
	A string `json:"a"`
	B string `json:"b"`
}

func unmarshaler(value interface{}) error {

	var err error
	data := `{"a":"beep","b":"boop"}`
	switch value := value.(type) {

	case nil:
	case *string:
		fmt.Println("*string")
		*value = data
	case *[]byte:
		fmt.Println("*[]byte")
		*value = []byte(data)
	case encoding.TextUnmarshaler:
		fmt.Println("encoding.TextUnmarshaler")
		err = value.UnmarshalText([]byte(data))
	default:
		fmt.Println("default")
		err = json.Unmarshal([]byte(data), value)
	}

	return err
}