How to implement polymorphism and overloading in Go language?

As a statically typed language, Go language does not seem to be able to implement polymorphism and overloading like dynamic languages. However, the Go language uses the characteristics of interfaces to achieve polymorphism, and the implementation of overloading is simpler and more precise.

Methods to implement polymorphism

The interface in Go language can realize polymorphism during the calling process. The interface can describe the behavior of an object. Any type that implements all methods of the interface can be called It is an instance of this interface type. In this way, polymorphism can be achieved by simply defining the interface type and implementing different concrete types.

The following is a simple example that defines an interface that can output content, and many types, each of which implements the methods of this interface. Among them, the PrintContent function will only use the interface type as a parameter, but will adaptively call the PrintContent method of each type at runtime, showing the polymorphic characteristics.

// 定义一个输出内容的接口类型
type Printer interface {
    PrintContent()
}

// 三个实现该接口的类型
type Cat struct {
    Name string
}
func (c Cat) PrintContent() {
    fmt.Println("我的名字是", c.Name, "，我是猫")
}

type Dog struct {
    Name string
}
func (d Dog) PrintContent() {
    fmt.Println("我的名字是", d.Name, "，我是狗")
}

type Bird struct {
    Name string
}
func (b Bird) PrintContent() {
    fmt.Println("我的名字是", b.Name, "，我是鸟")
}

// 调用PrintContent方法，传入接口类型的参数
func PrintContent(p Printer) {
    p.PrintContent()
}

Methods to implement overloading

There is no native function overloading feature in the Go language, but by using function name interfaces with different parameters, overloading can be displayed more simply and understandably. The concept of loading.

The following is an example that defines two functions with different names but similar functions. Although the function names are different, the parameter types are different, which can be called method overloading. In this way, there is no need to consider whether the parameter types match when calling the code, and you can directly use the correct function name.

type Rectangle struct {
    Width  float64
    Height float64
}

type Circle struct {
    Radius float64
}

// 计算矩形面积
func Area(r Rectangle) float64 {
    return r.Width * r.Height
}

// 计算圆形面积
func AreaOfCircle(c Circle) float64 {
    return math.Pi * c.Radius * c.Radius
}

In addition, another common technique in the Go language is to use different parameter types for function polymorphism. This technique is similar to function overloading, but the parameter types are the same but the number of parameters is different. The following is an example:

type Animal struct {
    Name string
}

type Dog struct {
    Name string
}

type Cat struct {
    Name string
}

// 打招呼函数，参数类型相同不同，实现了函数多态
func Greet(a Animal) {
    fmt.Println("你好，", a.Name)
}
func GreetDog(d Dog) {
    fmt.Println("汪，汪，我是", d.Name)
}
func GreetCat(c Cat) {
    fmt.Println("喵，喵，我是", c.Name)
}

In this way, function polymorphism and overloading can be better realized, improving the readability and maintainability of the code.

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