update book code

eBook/exercises/chapter_10/inheritance_car.go

@@ -0,0 +1,59 @@
+// inheritance_car.go
+package main
+
+import (
+	"fmt"
+)
+
+type Engine interface {
+    Start()
+    Stop()
+}
+
+type Car struct {
+	wheelCount int
+	Engine
+}
+
+// define a behavior for Car
+func (car Car) numberOfWheels() int {
+    return car.wheelCount
+}
+
+type Mercedes struct {
+    Car //anonymous field Car
+}
+
+// a behavior only available for the Mercedes
+func (m *Mercedes) sayHiToMerkel() {
+    fmt.Println("Hi Angela!")
+}
+
+func (c *Car) Start() {
+	fmt.Println("Car is started")
+}
+
+func (c *Car) Stop() {
+	fmt.Println("Car is stopped")
+}
+
+func (c *Car) GoToWorkIn() {
+    // get in car 
+    c.Start();
+    // drive to work 
+    c.Stop();
+    // get out of car 
+}
+
+func main() {
+	m := Mercedes{Car{4, nil}}
+ 	fmt.Println("A Mercedes has this many wheels: ", m.numberOfWheels())
+	m.GoToWorkIn()
+	m.sayHiToMerkel()
+}
+/* Output:
+A Mercedes has this many wheels:  4
+Car is started
+Car is stopped
+Hi Angela!
+*/