repo.go

package main

import (
	"fmt"
	"log"
	"reflect"
	"time"
)


// User facing API. THE MOST IMPORTANT THING

type User struct {
	Name string
	Height float64
}

type Repository struct {
    ID          int        `json:"id"`
    Owner       User       `json:"owner"`
    Name        string     `json:"name"`
    Description string     `json:"description"`
    CreatedAt   time.Time  `json:"created_at"`
    PushedAt    time.Time  `json:"pushed_at"`
    UpdatedAt   time.Time  `json:"updated_at"`
}


// API for editing

type EditableRepository struct {
	Repository
	fields_to_update []string
}


// These are easily generated

func (r *EditableRepository) SetID(id int) {
	r.ID = id
	r.fields_to_update = append(r.fields_to_update, "ID")
}

func (r *EditableRepository) SetName(name string) {
	r.Name = name
	r.fields_to_update = append(r.fields_to_update, "Name")
}

func (r *EditableRepository) SetCreatedAt(date time.Time) {
	r.CreatedAt = date
	r.fields_to_update = append(r.fields_to_update, "CreatedAt")
}


// Get the type once
var rtype = reflect.TypeOf(Repository{})

func edit(user string, repo string, to_edit *EditableRepository) map[string]interface{} {
	json := make(map[string]interface{})
	for _, field := range to_edit.fields_to_update {
		sfield, found := rtype.FieldByName(field)
		if !found {
			log.Fatal("You didn't write that code by hand, did you?")
		}
		json_field := sfield.Tag.Get("json")
		rval := reflect.ValueOf(to_edit.Repository)
		json[json_field] = rval.FieldByName(field).Interface()
	}
	return json
}

func main() {
	r := EditableRepository{}
	r.SetID(123)
	r.SetName("name")
	r.SetCreatedAt(time.Now())
	result := edit("user", "repo", &r)
	fmt.Printf("%#v\n", result)
}

repo_output

map[string]interface {}{"id":123, "name":"name", "created_at":time.Time{sec:63540035905, nsec:0x107a2e5b, loc:(*time.Location)(0x170c00)}}