main.go

/*

Duck typing in golang example.

You can try it here: https://play.golang.org/p/kHRnpmA206r

*/

package main

import (
	"fmt"
	"reflect"
)

type Animal struct {
	Name string
}

func (a Animal) String() string {
	return fmt.Sprintf("<Animal %s>", a.Name)
}

func (a Animal) GetName() string {
	return a.Name
}


type Lion struct {
	Name string
}

func (l Lion) Roar() {
	fmt.Printf("RRRRRRoarghrrrrr! I'm %s!\n", l.Name)
}

func (l Lion) String() string {
	return fmt.Sprintf("<Lion %s>", l.Name)
}


type Named interface {
	GetName() string
}


type Roaring interface {
	Roar()
}


func genericRoar(x interface{}) {
	st := reflect.TypeOf(x)
	
	fmt.Printf("Type is %v\n\n", st)
	
	fmt.Println("Roaring using switch...")
	switch v := x.(type) {
	case Roaring:
		v.Roar()
	case Named:
		fmt.Printf("%s can't roar\n", v.GetName())
	default:
		fmt.Println("Can't roar")
	}
	
	fmt.Println("\nRoaring using reflection...")
	roar, ok := st.MethodByName("Roar")
	if !ok {
		switch v := x.(type) {
		case Named:
			fmt.Printf("%s can't roar\n", v.GetName())
		default:
    			fmt.Println("Can't roar")
		}
	} else {
		fmt.Printf("Roar method is %v\n", roar)
		x.(interface{Roar()}).Roar()
		
		reflect.ValueOf(x).MethodByName("Roar").Call([]reflect.Value{})
	}
}

func main() {
	a := &Animal{"Chuchundra"}
	fmt.Printf("Creature is %v\n", a)
	genericRoar(a)
	
	fmt.Println()
	l := &Lion{"Simba"}
	fmt.Printf("Creature is %v\n", l)
	genericRoar(l)
}