Custom Unmarshal

custom_unmarshal.go

package main

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

// 1st Implementation
type Blog1 struct {
	ThumbnailURL string `json:"thumbnailUrl"`
	Title        string `json:"title"`
	Tags         Tags   `json:"tags"`
}

type Tags []string

func (t *Tags) UnmarshalJSON(data []byte) error {
	var tags string

	err := json.Unmarshal(data, &tags)
	if err != nil {
		return err
	}

	*t = strings.Split(tags, ", ")

	return nil
}

// 2nd Implementation
type Blog2 struct {
	ThumbnailURL string   `json:"thumbnailUrl"`
	Title        string   `json:"title"`
	Tags         []string `json:"tags"`
}

func (b *Blog2) UnmarshalJSON(data []byte) error {
	type blog struct {
		ThumbnailURL string `json:"thumbnailUrl"`
		Title        string `json:"title"`
		Tags         string `json:"tags"`
	}

	var blg blog

	err := json.Unmarshal(data, &blg)
	if err != nil {
		return err
	}

	b.ThumbnailURL = blg.ThumbnailURL
	b.Title = blg.Title
	b.Tags = strings.Split(blg.Tags, ", ")

	return nil
}

func main() {
	blogJSON := `{"thumbnailUrl": "https://assets.sujames.com/blogs/511a21c4-c923-42fd-996a-10c7ca114f77", "title": "ทำ Custom Unmarshal ใน Go กันเถอะ!", "tags": "Golang, Custom Unmarshal, JSON"}`

	err := unmarshalBlog1([]byte(blogJSON))
	if err != nil {
		// handle error
	}

	err = unmarshalBlog2([]byte(blogJSON))
	if err != nil {
		// handle error
	}
}

func unmarshalBlog1(blogJSON []byte) error {
	var b Blog1

	err := json.Unmarshal(blogJSON, &b)
	if err != nil {
		return err
	}

	for i, t := range b.Tags {
		fmt.Printf("[blog1] at index %d: %s\n", i, t)
	}

	return nil
}

func unmarshalBlog2(blogJSON []byte) error {
	var b Blog2

	err := json.Unmarshal(blogJSON, &b)
	if err != nil {
		return err
	}

	for i, t := range b.Tags {
		fmt.Printf("[blog2] at index %d: %s\n", i, t)
	}

	return nil
}