update: powerdrawer interface

interfaces/04-interfaces/power/blender.go

@@ -0,0 +1,20 @@
+// 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"
+)
+
+// Blender can be powered
+type Blender struct{}
+
+// Draw power to a Blender
+func (Blender) Draw(power int) {
+	fmt.Printf("Blender is drawing %dkW of electrical power.\n", power)
+}

interfaces/04-interfaces/power/kettle.go

@@ -0,0 +1,20 @@
+// 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"
+)
+
+// 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)
+}

interfaces/04-interfaces/power/main.go

@@ -13,52 +13,38 @@ import (
 	"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)
-}
-
-// -----
+// RUN IT WITH ALL THE FILES IN THE DIRECTORY LIKE SO:
+// go run .
 
 func main() {
 	rand.Seed(time.Now().UnixNano())
 
-	kettle := Kettle{}
-	mixer := Mixer{}
+	var (
+		blender Blender
+		player  Player
+		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)
+
+	if err := socket.Plug(blender); err != nil {
+		fmt.Println("Blender cannot be powered up:", err)
+	}
+
+	if err := socket.Plug(player); err != nil {
+		fmt.Println("Player cannot be powered up:", err)
+	}
+
+	if err := socket.Plug(kettle); err != nil {
+		fmt.Println("Kettle cannot be powered up:", err)
+	}
+
+	if err := socket.Plug(mixer); err != nil {
+		fmt.Println("Mixer cannot be powered up:", err)
+	}
 
 	fmt.Printf("Socket's available power is %d kW.\n", socket.power)
 }

interfaces/04-interfaces/power/mixer.go

@@ -0,0 +1,20 @@
+// 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"
+)
+
+// 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)
+}

interfaces/04-interfaces/power/player.go

@@ -0,0 +1,20 @@
+// 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"
+)
+
+// Player can be powered
+type Player struct{}
+
+// Draw power to a Player
+func (Player) Draw(power int) {
+	fmt.Printf("Player is drawing %dkW of electrical power.\n", power)
+}

interfaces/04-interfaces/power/socket.go

@@ -0,0 +1,38 @@
+// 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"
+)
+
+// PowerDrawer represents an electrical device that can draw power.
+// The power source doesn't have to be a Socket.
+type PowerDrawer interface {
+	Draw(power int)
+}
+
+// Socket has the power!
+type Socket struct {
+	power int
+}
+
+// Plug a device to draw power from the `Socket`
+func (s *Socket) Plug(device PowerDrawer) error {
+	n := rand.Intn(50) + 1
+
+	if s.power-n <= 0 {
+		return fmt.Errorf("socket is out of power for %dkW", n)
+	}
+
+	s.power -= n
+	device.Draw(n)
+
+	return nil
+}