golang interface receiver

interface Animal作為資料類型構建的slice：

package main

import (

    "fmt"

)

type Animal interface {

    Speak() string

}

type Dog struct {}

func (d Dog) Speak() string

{

    return "Woof!"

}

type Cat struct {}

//1func (c *Cat) Speak() string {

    return "Meow!"

}

type Llama struct {}

func (l Llama) Speak() string

{

    return "?????"

}

type JavaProgrammer struct {}

func (j JavaProgrammer) Speak() string {

    return "Design patterns!"

}

func main() {

    animals := []Animal{Dog{}, Cat{}, Llama{}, JavaProgrammer{}}

    for _, animal := range animals {

        fmt.Println(animal.Speak())

    }

}

輸出:

prog.go:33:32: cannot use Cat literal (type Cat) as type Animal in array or slice literal:

Cat does not implement Animal (Speak method has pointer receiver)