add: reflection decoder

interfaces/11-reflection-decoder/book.go

@@ -0,0 +1,53 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"time"
+)
+
+type book struct {
+	product
+	Published interface{}
+}
+
+func (b book) String() string {
+	p := format(b.Published)
+	return fmt.Sprintf("%s - (%v)", &b.product, p)
+}
+
+func (b *book) MarshalJSON() ([]byte, error) {
+	type jbook book
+
+	jb := (*jbook)(b)
+	jb.Published = format(b.Published)
+
+	return json.Marshal(jb)
+}
+
+func format(v interface{}) string {
+	var t int
+
+	switch v := v.(type) {
+	case int:
+		t = v
+	case string:
+		t, _ = strconv.Atoi(v)
+	default:
+		return "unknown"
+	}
+
+	// Mon Jan 2 15:04:05 -0700 MST 2006
+	const layout = "2006/01"
+
+	u := time.Unix(int64(t), 0)
+	return u.Format(layout)
+}

interfaces/11-reflection-decoder/database.json

@@ -0,0 +1,54 @@
+[
+	{
+		"Category": "book",
+		"Item": {
+			"Title": "moby dick",
+			"Price": 10,
+			"Published": "1973/10"
+		}
+	},
+	{
+		"Category": "book",
+		"Item": {
+			"Title": "odyssey",
+			"Price": 15,
+			"Published": "1993/04"
+		}
+	},
+	{
+		"Category": "book",
+		"Item": {
+			"Title": "hobbit",
+			"Price": 25,
+			"Published": "unknown"
+		}
+	},
+	{
+		"Category": "puzzle",
+		"Item": {
+			"Title": "rubik's cube",
+			"Price": 5
+		}
+	},
+	{
+		"Category": "game",
+		"Item": {
+			"Title": "minecraft",
+			"Price": 20
+		}
+	},
+	{
+		"Category": "game",
+		"Item": {
+			"Title": "tetris",
+			"Price": 5
+		}
+	},
+	{
+		"Category": "toy",
+		"Item": {
+			"Title": "yoda",
+			"Price": 150
+		}
+	}
+]

interfaces/11-reflection-decoder/decoder.go

@@ -0,0 +1,63 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "encoding/json"
+
+type decoderSchema struct {
+	Category string
+
+	// json.RawMessage is a special type of the json package.
+	// It prevents the json package functions encode/decode
+	// the specific parts of the json data.
+	Item json.RawMessage
+}
+
+func decode(data []byte) (list, error) {
+	var schemas []decoderSchema
+
+	if err := json.Unmarshal(data, &schemas); err != nil {
+		return nil, err
+	}
+
+	return toStore(schemas)
+}
+
+func toStore(schemas []decoderSchema) (store list, err error) {
+	for _, s := range schemas {
+		p := newProduct(s.Category)
+
+		if json.Unmarshal(s.Item, &p); err != nil {
+			return nil, err
+		}
+
+		store = append(store, p)
+	}
+	return store, nil
+}
+
+func newProduct(category string) item {
+	// for each product you need to open this code
+	// and add a new case.
+	//
+	// dependency injection should be the responsibility
+	// of the user of this function.
+	switch category {
+	case "book":
+		// var b book
+		// return &b
+		return new(book)
+	case "game":
+		return new(game)
+	case "puzzle":
+		return new(puzzle)
+	case "toy":
+		return new(toy)
+	}
+	return nil
+}

interfaces/11-reflection-decoder/game.go

@@ -0,0 +1,12 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+type game struct {
+	product
+}

interfaces/11-reflection-decoder/list.go

@@ -0,0 +1,59 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type item interface {
+	discount(float64)
+	fmt.Stringer
+}
+
+type schema struct {
+	Category string
+	Item     item
+}
+
+type list []item
+
+func (l list) MarshalJSON() ([]byte, error) {
+	var schemas []schema
+
+	for _, it := range l {
+		cat := reflect.TypeOf(it).Elem().Name()
+		schemas = append(schemas, schema{cat, it})
+	}
+
+	return json.Marshal(schemas)
+}
+
+func (l list) String() string {
+	if len(l) == 0 {
+		return "Sorry. We're waiting for delivery 🚚."
+	}
+
+	var str strings.Builder
+
+	for _, it := range l {
+		str.WriteString(it.String())
+		str.WriteRune('\n')
+	}
+
+	return str.String()
+}
+
+func (l list) discount(ratio float64) {
+	for _, it := range l {
+		it.discount(ratio)
+	}
+}

interfaces/11-reflection-decoder/main.go

@@ -0,0 +1,31 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+)
+
+func main() {
+	data, err := ioutil.ReadFile("database.json")
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	store, err := decode(data)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	fmt.Print(store)
+	// for _, p := range store {
+	// 	fmt.Printf("%#v\n", p)
+	// }
+}

interfaces/11-reflection-decoder/money.go

@@ -0,0 +1,16 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "fmt"
+
+type money float64
+
+func (m money) String() string {
+	return fmt.Sprintf("$%.2f", m)
+}

interfaces/11-reflection-decoder/product.go

@@ -0,0 +1,25 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+)
+
+type product struct {
+	Title string
+	Price money
+}
+
+func (p *product) String() string {
+	return fmt.Sprintf("%-15s: %s", p.Title, p.Price)
+}
+
+func (p *product) discount(ratio float64) {
+	p.Price *= money(1 - ratio)
+}

interfaces/11-reflection-decoder/puzzle.go

@@ -0,0 +1,12 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+type puzzle struct {
+	product
+}

interfaces/11-reflection-decoder/toy.go

@@ -0,0 +1,12 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+type toy struct {
+	product
+}