GO接口小记

Go语言中，任何类型都是空接口类型的实现类型。

声明：

类型实例 := new(某实现接口的类型) // 或者 `var 类型实例接口类型`，然后`类型实例 = new(某实现接口的类型)`

调用：

类型实例.接口方法()

某类型实现接口方法：

func (某类型) 方法名() {

方法内容

}

func (d *D) click() {
   fmt.Println("knock, ", d.Age)
}

重新回顾之后，其实是把类型new出来的实例(返回值是指针)，赋值给接口(不赋值也可以)，然后调用接口的方法。

直接 `var a 某个接口类型` 的话，得到的a的类型是nil

type E interface {
   click()
}

func main() {
    var cc E
    fmt.Printf("cc type is %T\n", cc)
}

cc type is <nil>

必须接口方法全部实现才可以赋值，否则编译会报错缺少某些方法

package main
import "fmt"

type Human struct {
    name string
    age int
    phone string
}

type Student struct {
    Human //匿名字段
    school string
    loan float32
}

type Employee struct {
    Human //匿名字段
    company string
    money float32
}

//Human实现SayHi方法
func (h Human) SayHi() {
    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
}

//Human实现Sing方法
func (h Human) Sing(lyrics string) {
    fmt.Println("La la la la...", lyrics)
}

//Employee重载Human的SayHi方法
func (e Employee) SayHi() {
    fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
e.company, e.phone)
    }

// Interface Men被Human,Student和Employee实现
// 因为这三个类型都实现了这两个方法
type Men interface {
    SayHi()
    Sing(lyrics string)
}

func main() {
    mike := Student{Human{"Mike", 25, "222-222-XXX"}, "MIT", 0.00}
    paul := Student{Human{"Paul", 26, "111-222-XXX"}, "Harvard", 100}
    sam := Employee{Human{"Sam", 36, "444-222-XXX"}, "Golang Inc.", 1000}
    tom := Employee{Human{"Tom", 37, "222-444-XXX"}, "Things Ltd.", 5000}

    //定义Men类型的变量i
    var i Men

    //i能存储Student
    i = mike
    fmt.Println("This is Mike, a Student:")
    i.SayHi()
    i.Sing("November rain")

    //i也能存储Employee
    i = tom
    fmt.Println("This is tom, an Employee:")
    i.SayHi()
    i.Sing("Born to be wild")

    //定义了slice Men
    fmt.Println("Let's use a slice of Men and see what happens")
    x := make([]Men, 3)
    //这三个都是不同类型的元素，但是他们实现了interface同一个接口
    x[0], x[1], x[2] = paul, sam, mike

    for _, value := range x{
        value.SayHi()
    }
}

结果如下：

This is Mike, a Student:

Hi, I am Mike you can call me on 222-222-XXX

La la la la... November rain

This is tom, an Employee:

Hi, I am Tom, I work at Things Ltd.. Call me on 222-444-XXX

La la la la... Born to be wild

Let's use a slice of Men and see what happens

Hi, I am Paul you can call me on 111-222-XXX

Hi, I am Sam, I work at Golang Inc.. Call me on 444-222-XXX

Hi, I am Mike you can call me on 222-222-XXX

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