update: marshaler interface

interfaces/10-marshaler/book.go

@@ -13,9 +13,11 @@ import (
 
 type book struct {
 	product
+
+	// Published (timestamp) knows how to print, encode and decode itself.
 	Published timestamp
 }
 
-func (b book) String() string {
+func (b *book) String() string {
 	return fmt.Sprintf("%s - (%s)", &b.product, b.Published)
 }

interfaces/10-marshaler/list.go

@@ -8,9 +8,7 @@
 package main
 
 import (
-	"encoding/json"
 	"fmt"
-	"reflect"
 	"strings"
 )
 
@@ -19,42 +17,14 @@ type item interface {
 	fmt.Stringer
 }
 
-// schema adds an additional category field
-// to the product types.
-type schema struct {
-	// Category is the product category field.
-	Category string
-
-	// Item is an interface value.
-	// Here, we are embedding an interface value.
-	Item item
-}
-
 type list []item
 
-// MarshalJSON is an implementation of the json.Marshaler interface.
-// json.Marshal and Decode call this method.
-func (l list) MarshalJSON() ([]byte, error) {
-	var schemas []schema
-
-	for _, it := range l {
-		// TypeOf -> finds the dynamic type of "it"
-		// Elem   -> returns the element type of the pointer
-		// Name   -> returns the type name as string
-		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')

interfaces/10-marshaler/main.go

@@ -14,85 +14,35 @@ import (
 )
 
 func main() {
-	// store := list{
-	// 	&book{product{"moby dick", 10}, 118281600},
-	// 	&book{product{"odyssey", 15}, "733622400"},
-	// 	&book{product{"hobbit", 25}, nil},
-	// 	&puzzle{product{"rubik's cube", 5}},
-	// 	&game{product{"minecraft", 20}},
-	// 	&game{product{"tetris", 5}},
-	// 	&toy{product{"yoda", 150}},
-	// }
-
-	// out, err := json.MarshalIndent(store, "", "\t")
-	// if err != nil {
-	// 	log.Fatalln(err)
-	// }
-	// fmt.Println(string(out))
-
-	// store.discount(.5)
-	// fmt.Print(store)
-
-	encode()
-}
-
-func encode() {
-
-	books := []*book{
-		{product{"moby dick", 10}, toTime(118281600)},
-		{product{"odyssey", 15}, toTime("733622400")},
-		{product{"hobbit", 25}, zeroTimestamp},
+	store := list{
+		&book{product{"moby dick", 10}, toTimestamp(118281600)},
+		&book{product{"odyssey", 15}, toTimestamp("733622400")},
+		&book{product{"hobbit", 25}, unknown},
+		&puzzle{product{"rubik's cube", 5}},
+		&game{product{"minecraft", 20}},
+		&game{product{"tetris", 5}},
+		&toy{product{"yoda", 150}},
 	}
 
-	for _, b := range books {
-		fmt.Println(b)
-	}
-
-	out, err := json.MarshalIndent(books, "", "\t")
+	out, err := json.MarshalIndent(store, "", "\t")
 	if err != nil {
 		log.Fatalln(err)
 	}
 
 	fmt.Println(string(out))
-}
-
-func decode() {
-	// books = nil
-	out := []byte(`[
-	{
-		"Title": "moby dick",
-		"Price": 10,
-		"Published": "118281600"
-	},
-	{
-		"Title": "odyssey",
-		"Price": 15,
-		"Published": 733622400
-	},
-	{
-		"Title": "hobbit",
-		"Price": 25,
-		"Published": -62135596800
-	},
-	{
-		"Title": "poka",
-		"Price": 25,
-		"Published": "1983/03"
-	},
-	{
-		"Title": "fuka",
-		"Price": 25
-	}	
-]`)
-
-	var books []*book
-
-	err := json.Unmarshal(out, &books)
-	if err != nil {
-		log.Fatalln(err)
-	}
-
-	for _, b := range books {
-		fmt.Println(b)
-	}
+
+	// store.discount(.5)
+	// fmt.Print(store)
+
+	// ----
+
+	// var ts timestamp
+	// json.Unmarshal([]byte(`118281600`), &ts)
+	// fmt.Println(ts)
+
+	// json.Unmarshal([]byte(`"18281600"`), &ts)
+	// fmt.Println(ts)
+
+	// json.Unmarshal([]byte(`"incorrect"`), &ts)
+	// fmt.Println(ts)
 }

interfaces/10-marshaler/product.go

@@ -7,9 +7,7 @@
 
 package main
 
-import (
-	"fmt"
-)
+import "fmt"
 
 type product struct {
 	Title string

interfaces/10-marshaler/timestamp.go

@@ -0,0 +1,77 @@
+// 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 (
+	"strconv"
+	"time"
+)
+
+// Mon Jan 2 15:04:05 -0700 MST 2006
+const layout = "2006/01"
+
+// unknown is the zero value of a timestamp.
+var unknown = timestamp(time.Time{})
+
+// timestamp prints timestamps, it's a stringer.
+// It is useful even if it's zero.
+type timestamp time.Time
+
+// MarshalJSON is an implementation of the json.Marshaler interface.
+// json.Marshal and json.Encode call this method.
+func (ts timestamp) MarshalJSON() (out []byte, err error) {
+	u := time.Time(ts).Unix()
+	return strconv.AppendInt(out, u, 10), nil
+}
+
+// UnmarshalJSON is an implementation of the json.Unmarshaler interface.
+// json.Unmarshal and json.Decode call this method.
+func (ts *timestamp) UnmarshalJSON(data []byte) error {
+	s := string(data)
+
+	// Let the ParseInt parse quoted strings.
+	us, err := strconv.Unquote(s)
+	if err == nil {
+		s = us
+	}
+
+	// Always overwrite the timestamp when decoding.
+	*ts = unknown
+
+	// Handle the numeric case.
+	if n, err := strconv.ParseInt(s, 10, 64); err == nil {
+		*ts = timestamp(time.Unix(n, 0))
+	}
+
+	return nil
+}
+
+func (ts timestamp) String() string {
+	t := time.Time(ts)
+
+	if t.IsZero() {
+		return "unknown"
+	}
+
+	return t.Format(layout)
+}
+
+func toTimestamp(v interface{}) timestamp {
+	var t int
+
+	switch v := v.(type) {
+	case int:
+		t = v
+	case string:
+		t, _ = strconv.Atoi(v)
+	default:
+		return unknown
+	}
+
+	return timestamp(time.Unix(int64(t), 0))
+}