在C#中,接口是实现多态的方式之一,但是接口更侧重对象的能力,是一种规范。如果继承了接口,就必须按照接口的要求去实现这个接口。接口与接口之间是可以有继承,而且是多继承。而golang中的接口,是一组方法的集合体,duck-type programming的一种体现。

如果有一种动物能够想鸭子那样行走,叫的也像鸭子,那么我们认为这就是鸭子。

1.C#的接口

前文提到,C#的接口侧重于能力,好的接口功能(能力)单一,接口能继承接口,类能继承多个接口(多种能力),如果继承了接口,就必须全部实现。

1.1 接口定义

接下来我们定义一个运动员IPlayer的接口:

public interface IPlayer
{
    //接口可以定义属性
    string Name { get; set; }
    double Height { get; set; }
    int Age { get; set; }
    
    //运动
    void PlaySport();
}

1.2 接口继承接口

再定义一个职业篮球运动员接口IBasketPlayer

  • 首先职业篮球运动员也是一个运动员,所以继承运动员接口IPlayer
  • 其次,不管是哪个联赛的职业运动员,除了有一些通用的技术能力,都会面临转会事件TransferEvent
public interface IBasketPlayer: IPlayer
{
        //臂展
        double Wingspan { get; }

        //垂直摸高
        double Verticalreach { get; }

        //垂直跳跃
        double Verticalleap { get; }

        //索引器  为了演示,强行加一个索引器
        string this[string index]
        {
            get; set;
        }

        event EventHandler TransferEvent;


        //扣篮
        void Dunk();
        //传球
        void Pass();
        void Dribble();
        //3分球
        void ThreePointShot();
        //中远距离
        void TwoPointShot();
        //空接
        void AlleyOop();
        //篮板
        void Backboard();
}

1.3 实现接口

  • 定义一个NBA球员 NBAPlayer
public class NBAPlayer : IBasketPlayer
{
    //索引器
    public string this[string index] { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //臂展
    public double Wingspan => throw new NotImplementedException();
    
    //垂直摸高
    public double Verticalreach => throw new NotImplementedException();
    
    //垂直起跳
    public double Verticalleap => throw new NotImplementedException();
    
    //姓名
    public string Name { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //身高
    public double Height { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //年龄
    public int Age { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }

    public event EventHandler TransferEvent;

    public void AlleyOop()
    {
        throw new NotImplementedException();
    }

    public void Backboard()
    {
        throw new NotImplementedException();
    }

    public void Dribble()
    {
        throw new NotImplementedException();
    }

    public void Dunk()
    {
        throw new NotImplementedException();
    }

    public void Pass()
    {
        throw new NotImplementedException();
    }

    public void PlaySport()
    {
        throw new NotImplementedException();
    }

    public void ThreePointShot()
    {
        throw new NotImplementedException();
    }

    public void TwoPointShot()
    {
        throw new NotImplementedException();
    }
}
  • 在定义一个CBA球员 实现接口CBAPlayer
public class CBAPlayer : IBasketPlayer
{
    //索引器
    public string this[string index] { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //臂展
    public double Wingspan => throw new NotImplementedException();
    
    //锤子摸高
    public double Verticalreach => throw new NotImplementedException();
    
    //垂直起跳
    public double Verticalleap => throw new NotImplementedException();
    
    //姓名
    public string Name { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //身高
    public double Height { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //年龄
    public int Age { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }

    //转会事件
    public event EventHandler TransferEvent;

    public void AlleyOop()
    {
        throw new NotImplementedException();
    }

    public void Backboard()
    {
        throw new NotImplementedException();
    }

    public void Dribbl()
    {
        throw new NotImplementedException();
    }

    public void Dunk()
    {
        throw new NotImplementedException();
    }

    public void Pass()
    {
        throw new NotImplementedException();
    }

    public void PlaySport()
    {
        throw new NotImplementedException();
    }

    public void ThreePointShot()
    {
        throw new NotImplementedException();
    }

    public void TwoPointShot()
    {
        throw new NotImplementedException();
    }
}

1.4 实现多个接口

NBA很多黑人球员,不但会打篮球,还会说唱,(黑人,人均会跳舞,会说唱,^_^),比较有名的有艾弗森,阿泰斯特,利拉德,尤其是艾弗森Allen Iverson,很多音乐平台都能搜到,但是CBA球员就不一定会说唱,所以继续定义一个说唱接口 IRapper

public interface IRapper
{
    void Rapper();
}
public class NBAPlayer : IBasketPlayer,IRapper
{
    //索引器
    public string this[string index] { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //臂展
    public double Wingspan => throw new NotImplementedException();
    
    //锤子摸高
    public double Verticalreach => throw new NotImplementedException();
    
    //垂直起跳
    public double Verticalleap => throw new NotImplementedException();
    
    //姓名
    public string Name { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //身高
    public double Height { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
    
    //年龄
    public int Age { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }

    //转会
    public event EventHandler TransferEvent;
    
    //会说唱
    public void Rapper()
    {
        throw new NotImplementedException();
    }
    

    public void AlleyOop()
    {
        throw new NotImplementedException();
    }

    public void Backboard()
    {
        throw new NotImplementedException();
    }

    public void Dribbl()
    {
        throw new NotImplementedException();
    }

    public void Dunk()
    {
        throw new NotImplementedException();
    }

    public void Pass()
    {
        throw new NotImplementedException();
    }

    public void PlaySport()
    {
        throw new NotImplementedException();
    }

    public void ThreePointShot()
    {
        throw new NotImplementedException();
    }

    public void TwoPointShot()
    {
        throw new NotImplementedException();
    }
}

2.Golang的接口

C#的接口可以说一种规范,它可以包含数据的规范,比如属性,事件,索引器,也可以包含行为(方法)的规范,但是Golang有所不同:Golang不关心数据,只关心行为(方法)。

2.1 接口定义

接口是一种类型,抽象类型,就像定义struct一样定义:

type Player interface {
	PlaySport()
}

2.2 实现接口

一个对象(能作为方法的接收者)只要实现了接口中定义的方法,那么就算实现了这个接口。

func main(){
    var player Player = &NBAPlayer{
        Name: "James",
    }

	player.PlaySport()
}
type Player interface {
	PlaySport()
}
type NBAPlayer struct {
	Name          string
	Height        float32
	Age           int8
	Wingspan      float32
	Verticalreach float32
	Verticalleap  float32
}
//指针接收者实现接口
func (p *NBAPlayer) PlaySport() {
	fmt.Println(p.Name, "从事的运动项目是打篮球")
}
James 从事的运动项目是打篮球

ps:如果是上面的代码采用值接收者func (p NBAPlayer) PlaySport(),无论是结构体还是结构体指针都可以赋值给接口变量,因为Go语言中有对指针类型变量求值的语法糖,结构体指针内部会自动求值*struct。如果是上面代码那样采用指针接收者,那么接口变量就必须传指针。这个问题如果不熟练,会在实际编码中一次次被编译器打脸。

2.3 实现多个接口

一个NBA球员既要实现Player接口,又要实现Rapper接口:

func main(){
    var player Player = &NBAPlayer{
        Name: "James",
    }
	var rapper Rapper = &NBAPlayer{
		Name: "James",
	}

	player.PlaySport()
	rapper.Rapper()
}
type Rapper interface {
	Rapper()
}
type Player interface {
	PlaySport()
}
type NBAPlayer struct {
	Name          string
	Height        float32
	Age           int8
	Wingspan      float32
	Verticalreach float32
	Verticalleap  float32
}
//指针接收者实现接口
func (p *NBAPlayer) PlaySport() {
	fmt.Println(p.Name, "从事的运动项目是打篮球")
}
func (p *NBAPlayer) Rapper() {
	fmt.Println(p.Name, "还会说唱")
}
James 从事的运动项目是打篮球
James 还会说唱

2.4 嵌套接口

接口BasketPlayer嵌套接口Player,Rapper,这个就类似于C#接口可以继承接口。

func main(){
	var nbaplayer BasketPlayer = &NBAPlayer{
		Name: "Allen Iverson",
	}
	nbaer.PlaySport()
	nbaer.Rapper()
    nbaer.Dunk()
}
type BasketPlayer interface {
	Player
	Rapper
    Dunk()
}
func (p *NBAPlayer) PlaySport() {
	fmt.Println(p.Name, "从事的运动项目是打篮球")
}
func (p *NBAPlayer) Rapper() {
	fmt.Println(p.Name, "还会说唱")
}
func (p *NBAPlayer) Dunk() {
	fmt.Println(p.Name, "会扣篮")
}
Allen Iverson 从事的运动项目是打篮球
Allen Iverson 还会说唱
Allen Iverson 会扣篮

2.5* 空接口

空接口是指没有定义任何方法的接口。**因此任何类型都实现了空接口。**套用周星驰电影的台词,”其实根本没有什么空接口,或许一切都是都是空接口“,空接口类型的变量可以存储任意类型的变量。

2.5.1 空接口切片

  • 看一下fmt包的Println方法,参数就是一个空接口的切片
func Println(a ...interface{}) (n int, err error) {
	return Fprintln(os.Stdout, a...)
}

2.5.2 保存任意值的map

  • 我们定义map make(map[TKey]TValue),当TValue换成interface{}空接口时,这时候的mapvalue就不再是单一的类型,而是可以为任意类型。
	var player = make(map[string]interface{})
	player["name"] = "LeBron James"
	player["age"] = 36

2.5.3 类型断言

类型断言主要用于判断空接口中的值,因为空接代表任意类型。x.(T)

var x interface{}
x = "randyfield"
v, ok := x.(string)
if ok {
    fmt.Println(v)
} else {
    fmt.Println("断言失败")
}

关于接口,不要为了接口而写接口,会增加不必要的抽象,导致不必要的运行时损耗。

再次强调:这个系列并不是教程,如果想系统的学习,博主可推荐学习资源。