一篇文章带你玩转go语言的接口

type Phone interface {
   call()
}
type Nokia struct {
    name string
}
// 接口的实现是隐式的
func (phone Nokia) call() {
    fmt.Println("我是 Nokia，是一台电话")
}

package main
import (
    "fmt"
    "strconv"
)
// 定义一个接口
type Good interface {
    settleAccount() int
    orderInfo() string
}
type Phone struct {
    name string
    quantity int
    price int
}
func (phone Phone) settleAccount() int {
    return phone.quantity * phone.price
}
func (phone Phone) orderInfo() string{
    return "您要购买" + strconv.Itoa(phone.quantity)+ "个" +
        phone.name + "计：" + strconv.Itoa(phone.settleAccount()) + "元"
}
type FreeGift struct {
    name string
    quantity int
    price int
}
func (gift FreeGift) settleAccount() int {
    return 0
}
func (gift FreeGift) orderInfo() string{
    return "您要购买" + strconv.Itoa(gift.quantity)+ "个" +
        gift.name + "计：" + strconv.Itoa(gift.settleAccount()) + "元"
}
func calculateAllPrice(goods []Good) int {
    var allPrice int
    for _,good := range goods{
        fmt.Println(good.orderInfo())
        allPrice += good.settleAccount()
    }
    return allPrice
}
func main()  {
    iPhone := Phone{
        name:     "iPhone",
        quantity: 1,
        price:    8000,
    }
    earphones := FreeGift{
        name:     "耳机",
        quantity: 1,
        price:    200,
    }
    goods := []Good{iPhone, earphones}
    allPrice := calculateAllPrice(goods)
    fmt.Printf("该订单总共需要支付 %d 元", allPrice)
}

package main
import (
    "fmt"
)
func main() {
    var i interface{}
    fmt.Printf("type: %T, value: %v", i, i)
}

// 声明一个空接口实例
    var i interface{}
    // 存 int 没有问题
    i = 1
    fmt.Println(i)
    // 存字符串也没有问题
    i = "hello"
    fmt.Println(i)
    // 存布尔值也没有问题
    i = false
    fmt.Println(i)

func main() {
    any := make([]interface{}, 5)
    any[0] = 11
    any[1] = "hello world"
    any[2] = []int{11, 22, 33, 44}
    for _, value := range any {
        fmt.Println(value)
    }
}

  // 声明a变量, 类型int, 初始值为1
    var a int = 1
    // 声明i变量, 类型为interface{}, 初始值为a, 此时i的值变为1
    var i interface{} = a
    // 声明b变量, 尝试赋值i  报错
    var b int = i

 sli := []int{2, 3, 5, 7, 11, 13}
    var i interface{}
    i = sli
     //报错
    g := i[1:3]
    fmt.Println(g)

这里还有一点要说明   空接口调用函数时的隐式转换
func myfunc(i interface{})  {
    switch i.(type) {
    case int:
        fmt.Println("参数的类型是 int")
    case string:
        fmt.Println("参数的类型是 string")
    }
}
func main() {
    a := 10
    b := "hello"
    myfunc(a)
    myfunc(b)
如果写在外面  则报错
/*switch a.(type) {
    case int:
        fmt.Println("参数的类型是 int")
    case string:
        fmt.Println("参数的类型是 string")
    }
*/
}