Flattening marshalled JSON structs with anonymous members in Go

Question

Given the following code: (reproduced here at play.golang.org.)

package main

import (
    "encoding/json"
    "fmt"
)

type User struct {         


        

Answer 1

I needed to do something similar and tried your technical of the embedded interface and (no surprise) had the same issue.

I didn't want to have to alter all the possible structs that needed additional fields, but ultimately I compromised with this solution:

http://play.golang.org/p/asLFPx76jw

package main

import (
    "encoding/json"
    "fmt"
)

type HateoasFields struct {
    Links []interface{} `json:"_links,omitempty"`
}

type User struct {
    Id   int    `json:"id"`
    Name string `json:"name"`
    HateoasFields
}

type Session struct {
    Id     int `json:"id"`
    UserId int `json:"userId"`
    HateoasFields
}

func main() {
    u := &User{Id: 123, Name: "James Dean"}
    s := &Session{Id: 456, UserId: 123}

    u.Links = []interface{}{fmt.Sprintf("http://user/%d", u.Id)}
    s.Links = []interface{}{fmt.Sprintf("http://session/%d", s.Id)}

    uBytes, _ := json.Marshal(u)
    sBytes, _ := json.Marshal(s)

    fmt.Println(string(uBytes))
    fmt.Println(string(sBytes))
}

Which outputs:

{"id":123,"name":"James Dean","_links":["http://user/123"]}
{"id":456,"userId":123,"_links":["http://session/456"]}

Rather than embedding the original structs in a struct with the additional fields, I did the opposite.

When looking at your original code, I don't think this solution is that awesome. How is this better than adding the Links property to the original struct? But for my app needs it was the best thing.