Go语言之Interface(二)

使用指针接收器和值接收器实现接口

type Describer interface {
    Describe()
}

type Person struct {
    name string
    age  int
}

func (p Person) Describe() {
    fmt.Printf("%s is %d years old\n", p.name, p.age)
}

type Address struct {
    state   string
    country string
}

func (a *Address) Describe() {
    fmt.Printf("State %s Country %s", a.state, a.country)
}

    var d1 Describer
    p1 := Person{"Sam", 25}
    d1 = p1
    d1.Describe()
    p2 := Person{"James", 39}
    d1 = &p2
    d1.Describe()

    var d2 Describer
    a := Address{"Beijing", "China"}
    d2 = &a
    d2.Describe()

实现多个接口

type NormalSalary interface {
    DisplaySalary()
}

type LevaeSalary interface {
    CalculateLeaveLeft() int
}

type Employee struct {
    firstName   string
    lastName    string
    basicPay    int
    pf          int
    totalLeaves int
    leavesTaken int
}

func (e Employee) DisplaySalary() {
    fmt.Printf("%s %s has salary $%d\n", e.firstName, e.lastName, (e.basicPay + e.pf))
}

func (e Employee) CalculateLeaveLeft() int {
    return e.totalLeaves - e.leavesTaken
}

    e := Employee{
        firstName:   "Kevin",
        lastName:    "Lee",
        basicPay:    5000,
        pf:          200,
        totalLeaves: 30,
        leavesTaken: 5,
    }

    var ns NormalSalary = e
    ns.DisplaySalary()

    var l LevaeSalary = e
    fmt.Println("Leaves left =", l.CalculateLeaveLeft())

接口嵌套

在Go语言中没有继承的概念，但是通过组合可以实现继承的效果

type NormalSalary interface {
    DisplaySalary()
}

type LevaeSalary interface {
    CalculateLeaveLeft() int
}

type SalaryOperator interface {
    NormalSalary
    LevaeSalary
}

    var empOp SalaryOperator = e
    empOp.DisplaySalary()
    fmt.Println("Leaves left = ", empOp.CalculateLeaveLeft())

接口零值

零值接口是nil,nil接口中的type和value都是nil

type Describer interface {
    Describe()
}

    var d4 Describer
    if d4 == nil {
        fmt.Printf("d4 is nil and has type %T value %v\n", d4, d4)
    }

输出结果是

d4 is nil and has type <nil> value <nil>