Go 中的指针和接口(interface)

Question

我想了解我在这里做错了什么..感谢所有回复:)

如果取消注释“//grow()”有效，

其他错误:

prog.go:38:2: impossible type switch case: p (type plant) cannot have dynamic type plant1 (grow method has pointer receiver) prog.go:39:16: impossible type assertion: plant1 does not implement plant (grow method has pointer receiver) prog.go:40:2: impossible type switch case: p (type plant) cannot have dynamic type plant2 (grow method has pointer receiver) prog.go:41:16: impossible type assertion: plant2 does not implement plant (grow method has pointer receiver) prog.go:60:12: cannot use p1 (type plant1) as type plant in argument to showHeight: plant1 does not implement plant (grow method has pointer receiver) prog.go:61:12: cannot use p2 (type plant2) as type plant in argument to showHeight: plant2 does not implement plant (grow method has pointer receiver)

https://play.golang.org/p/oMv7LdW85yK

package main

import (
    "fmt"
)

type plant1 struct {
    name   string
    height int
}

type plant2 struct {
    species string
    height  int
}

func (self *plant1) grow() {
    self.height++
}
func (self *plant2) grow() {
    self.height++
}

func (self plant1) getHeight() int {
    return self.height
}
func (self plant2) getHeight() int {
    return self.height
}

type plant interface {
    getHeight() int
    //grow()
}

func showHeight(p plant) {
    switch p.(type) {
    case plant1:
        fmt.Println(p.(plant1).name, `Height = `, p.(plant1).getHeight())
    case plant2:
        fmt.Println(p.(plant2).species, `Height = `, p.(plant2).getHeight())
    }

}

func main() {

    p1 := plant1{
        name:   `Plant 10`,
        height: 1,
    }
    p2 := plant2{
        species:   `Plant 20`,
        height: 1,
    }
    p1.grow()
    p1.grow()
    p2.grow()   

    showHeight(p1)
    showHeight(p2)
}

Answer 1

您包装到接口(interface)中的值不可寻址。该值必须可寻址才能调用指针接收器上的方法。 grow 方法是用指针接收器声明的。因此，编译器发现 plant 接口(interface)既不是由 plant1 类型实现的，也不是由 plant2 类型实现的。因此，您不能将 plant1 或 plant2 作为 plant 传递给 showHeight 函数。并且切换是不可能的，因为 plant 接口(interface)的实现不包括 plant1 和 plant2 类型。

参见 Why value stored in an interface is not addressable in Golang