golang接口(interface) "used as value"错误

Question

package main

import (
    "fmt"
)

type animal interface {
    speak()
}

type dog struct {
    name, sound  string
}

type cat struct {
    name, sound  string
}

func (d dog) speak() {
    fmt.Println(d.name, " goes ", d.sound)
}

func (c cat) speak() {
    fmt.Println(c.name, " goes ", c.sound)
}

func animal_speak(a animal) {
    fmt.Println(a.speak())
}

func main() {

    dogo := dog{"scooby", "woof"}
    cato := cat{"garfield", "meow"}

    animal_speak(dogo)
    animal_speak(cato)

}

当我调用动物界面时，出现以下错误

./interface.go:28:21: a.speak() used as value

我做错了什么？

Link to playground

Answer 1

接口(interface)不作为值使用。您正在使用不返回任何值的函数调用。

speak() 什么都不返回...那么您希望它打印什么？