update: interfaces lecture

interfaces/04-interfaces/list.go

@@ -22,6 +22,8 @@ func (l list) print() {
 	}
 
 	for _, it := range l {
+		// fmt.Printf("(%-10T) --> ", it)
+
 		it.print()
 
 		// you cannot access to the discount method of the game type.
@@ -29,3 +31,18 @@ func (l list) print() {
 		// it.discount(.5)
 	}
 }
+
+// PREVIOUS CODE:
+
+// type list []*game
+
+// func (l list) print() {
+// 	if len(l) == 0 {
+// 		fmt.Println("Sorry. Our store is closed. We're waiting for the delivery 🚚.")
+// 		return
+// 	}
+
+// 	for _, it := range l {
+// 		it.print()
+// 	}
+// }

interfaces/04-interfaces/main.go

@@ -15,15 +15,13 @@ func main() {
 		rubik     = puzzle{title: "rubik's cube", price: 5}
 	)
 
+	// thanks to the printer interface we can add different types of values
+	// to the list.
+	//
+	// only rule: they need to implement the `printer` interface.
+	// to do that: each type needs to have a print method.
+
 	var store list
 	store = append(store, &minecraft, &tetris, mobydick, rubik)
-
-	tetris.discount(.8)
-	// printer(tetris).discount(.8)
 	store.print()
-
-	// p can store a value of any type that has a `print()` method
-	var p printer
-	p = puzzle{title: "sidewinder", price: 10}
-	p.print()
 }

interfaces/04-interfaces/power/main.go

@@ -0,0 +1,64 @@
+// 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"
+	"math/rand"
+	"time"
+)
+
+// Socket has the power!
+type Socket struct {
+	power int
+}
+
+// Plug a device to draw power from the `Socket`
+func (s *Socket) Plug(device PowerDrawer) {
+	n := rand.Intn(50)
+	s.power -= n
+	device.Draw(n)
+}
+
+// PowerDrawer can be any type that can be powered
+type PowerDrawer interface {
+	Draw(power int)
+}
+
+// -----
+
+// Kettle can be powered
+type Kettle struct{}
+
+// Draw power to a Kettle
+func (Kettle) Draw(power int) {
+	fmt.Printf("Kettle is drawing %dkW of electrical power.\n", power)
+}
+
+// Mixer can be powered
+type Mixer struct{}
+
+// Draw power to a Mixer
+func (Mixer) Draw(power int) {
+	fmt.Printf("Mixer is drawing %dkW of electrical power.\n", power)
+}
+
+// -----
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+
+	kettle := Kettle{}
+	mixer := Mixer{}
+
+	socket := &Socket{100}
+	socket.Plug(kettle)
+	socket.Plug(mixer)
+
+	fmt.Printf("Socket's available power is %d kW.\n", socket.power)
+}