努力查看接口类型的用途 [英] Struggling to See the Purpose of an Interface Type

问题描述

我最近很喜欢Go编程语言，到目前为止，我发现它很棒，但是确实很难理解接口.我已经阅读了很多有关它们的内容，但是对我来说它们仍然很抽象.

I've recently taken a liking to the Go programming language, I've found it wonderful so far but am really struggling to understand interfaces. I've read about quite a bit about them, but they still seem very abstract to me.

我编写了一些使用下面的接口的快速代码:

I've wrote a quick bit of code that uses an interface below:

package main

import (
  "fmt"
  "math"
)

type Circer interface {
    Circ() float64
}

type Square struct {
    side float64
}

type Circle struct {
    diam, rad float64
}

func (s *Square) Circ() float64 {
    return s.side * 4
}

func (c *Circle) Circ() float64 {
    return c.diam * math.Pi
}

func (c *Circle) Area() float64 {
    if c.rad == 0 {
        var rad = c.diam / 2
        return (rad*rad) * math.Pi
    } else {
        return (c.rad*c.rad) * math.Pi
    }
}

func main() {

    var s = new(Square)
    var c = new(Circle)

    s.side = 2
    c.diam = 10

    var i Circer = s

    fmt.Println("Square Circ: ", i.Circ())

    i = c

    fmt.Println("Circle Circ: ", i.Circ())
}

我真的看不到Circer界面的用途.这些方法已经编写好了，我可以通过直接在结构上直接调用它们而不是使用Circer作为包装器来保存两行代码.

I can't really see the purpose of the Circer interface. The methods are already written and I could save two lines of code by simply calling them directly on the structs, rather than using Circer as a wrapper.

有什么我想念的吗?我使用接口不正确吗?任何帮助或示例，不胜感激.

Is there something I'm missing? Am I using the interface incorrectly? Any help or examples are appreciated.

推荐答案

接口的要点是，您可以创建通用功能，例如下面的ShowMeTheCircumference.

The point of interfaces is that you can make general purpose functions like ShowMeTheCircumference below.

package main

import (
    "fmt"
    "math"
)

type Circer interface {
    Circ() float64
}

type Square struct {
    side float64
}

type Circle struct {
    diam, rad float64
}

func (s *Square) Circ() float64 {
    return s.side * 4
}

func (c *Circle) Circ() float64 {
    return c.diam * math.Pi
}

func ShowMeTheCircumference(name string, shape Circer) {
    fmt.Printf("Circumference of %s is %f\n", name, shape.Circ())
}

func main() {
    square := &Square{side: 2}
    circle := &Circle{diam: 10}
    ShowMeTheCircumference("square", square)
    ShowMeTheCircumference("circle", circle)

}

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