add: method embedding

interfaces/08-method-embedding/book.go

@@ -0,0 +1,60 @@
+// 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"
+	"strconv"
+	"time"
+)
+
+type book struct {
+	// embed the product type into the book type.
+	// all the fields and methods of the product will be
+	// available in this book type.
+	product
+	published interface{}
+}
+
+// book type's print method takes priority.
+//
+// + when you call it on a book value, the following method will
+//   be executed.
+//
+// + if it wasn't here, the product type's print method would
+//   have been executed.
+func (b *book) print() {
+	// the book can also call the embedded product's print method
+	// if it wants to, as in here:
+	b.product.print()
+
+	p := format(b.published)
+	fmt.Printf("\t - (%v)\n", p)
+}
+
+func format(v interface{}) string {
+	var t int
+
+	switch v := v.(type) {
+	case int:
+		// book{title: "moby dick", price: 10, published: 118281600},
+		t = v
+	case string:
+		// book{title: "odyssey", price: 15, published: "733622400"},
+		t, _ = strconv.Atoi(v)
+	default:
+		// book{title: "hobbit", price: 25},
+		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/08-method-embedding/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/08-method-embedding/list.go

@@ -0,0 +1,39 @@
+// 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 printer interface {
+	print()
+}
+
+type list []printer
+
+func (l list) print() {
+	if len(l) == 0 {
+		fmt.Println("Sorry. We're waiting for delivery 🚚.")
+		return
+	}
+
+	for _, it := range l {
+		it.print()
+	}
+}
+
+func (l list) discount(ratio float64) {
+	type discounter interface {
+		discount(float64)
+	}
+
+	for _, it := range l {
+		if it, ok := it.(discounter); ok {
+			it.discount(ratio)
+		}
+	}
+}

interfaces/08-method-embedding/main.go

@@ -0,0 +1,29 @@
+// 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
+
+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}},
+	}
+
+	store.discount(.5)
+	store.print()
+
+	// t := &toy{product{"yoda", 150}}
+	// fmt.Printf("%#v\n", t)
+
+	// b := &book{product{"moby dick", 10}, 118281600}
+	// fmt.Printf("%#v\n", b)
+}

interfaces/08-method-embedding/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/08-method-embedding/product.go

@@ -0,0 +1,23 @@
+// 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) print() {
+	fmt.Printf("%-15s: %s\n", p.title, p.price.string())
+}
+
+func (p *product) discount(ratio float64) {
+	p.price *= money(1 - ratio)
+}

interfaces/08-method-embedding/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/08-method-embedding/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
+}