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duck typing

golang中实现某个接口不需要像其它语言使用 implemet 去继承实现，而是只要你的结构体包含接口所需的方法即可

package mainimport "fmt"type Person interface {talk()
}type XM struct {
}func (receiver XM) talk() {fmt.Println("I am XM")
}func main() {var p Personp = XM{}p.talk() // I am XM
}

nil不一定是空接口

初始化的接口是等于 nil的，接口底层其实有一个type来记录原始的struct，当某个struct赋值给接口时，接口会在type中记录该类型（就算是nil也会记录），此时接口打印出来是nil，但和nil并不相等

}type XM struct {
}func (X XM) talk() {fmt.Println("I am XM")
}func main() {var p Personif p == nil {fmt.Println("var p Person is nil") //var p Person is nil}var a *XMif a == nil {fmt.Println("var a *XM is nil") //var a *XM is nil}p = aif p != nil {fmt.Println("var p != nil") //var p != nil}fmt.Println(p) // <nil>
}

组合代替继承

通过内嵌组合来继承功能,XM匿名内嵌了Person，就具有了Person的能力

package mainimport "fmt"type Person struct {Name string
}func (receiver Person) Talk() {fmt.Printf("I am %s \n", receiver.Name)
}type XM struct {Person
}func main() {var xm XMp := Person{Name: "Person"}xm.Name = "XM"xm.Talk() // I am XMp.Talk()  // I am Person
}

重写方法只需要声明一个同名方法即可

package mainimport "fmt"type Person struct {Name string
}func (receiver Person) Talk() {fmt.Printf("I am %s \n", receiver.Name)
}type XM struct {Person
}func (receiver XM) Talk() {fmt.Printf("hello,I am %s", receiver.Name)
}func main() {var xm XMxm.Name = "XM"xm.Talk() // hello,I am XM
}

接口转换回具体的类型

struct 转为接口，只要struct 拥有 接口的方法，即可将struct 赋值给接口，如果想将接口转回struct，可以使用 result,ok := interface.(struct), ok 代表是否能够成功转换

package mainimport "fmt"type IAnimal interface {Eat()
}type Bridge struct {
}func (b Bridge) Eat() {fmt.Println("I can eat")
}func (b Bridge) Fly() {fmt.Println("I can fly")
}type Fish struct {
}func (f Fish) Eat() {fmt.Println("I can eat")
}func ShowTime(animal IAnimal) {animal.Eat()if b, ok := animal.(Bridge); ok {b.Fly()}
}func main() {var (f Fishb Bridge)ShowTime(f) // I can eatfmt.Println("--------------")ShowTime(b) // I can eat \n I can fly
}

ok 判断的是完全转换，就算不ok，转换后的结果也可以调用struct的方法，但是不建议这么做

package mainimport "fmt"type IAnimal interface {Eat()
}type Bridge struct {Name string
}func (b Bridge) Eat() {fmt.Println(b.Name + "I can eat")
}func (b Bridge) Fly() {fmt.Println(b.Name + "I can fly")
}type Fish struct {Name string
}func (f Fish) Eat() {fmt.Println(f.Name + "I can eat")
}func ShowTime(animal IAnimal) {animal.Eat()b, ok := animal.(Bridge)fmt.Println(ok)b.Fly()
}func main() {f := Fish{Name: "fish"}b := Bridge{Name: "bridge"}ShowTime(f)// fishI can eat// false// I can flyfmt.Println("--------------")ShowTime(b)//bridgeI can eat// true//bridgeI can fly
}

使用switch匹配接口的原始类型

struct.(type) 可以获取接口的原始类型，但是只能在switch中使用

package mainimport "fmt"type IAnimal interface {Eat()
}type Bridge struct {Name string
}func (b Bridge) Eat() {fmt.Println(b.Name + "I can eat")
}func (b Bridge) Fly() {fmt.Println(b.Name + "I can fly")
}type Fish struct {Name string
}func (f Fish) Eat() {fmt.Println(f.Name + "I can eat")
}func ShowTime(animal IAnimal) {switch animal.(type) {case Fish:fmt.Println("原先是Fish")case Bridge:fmt.Println("原先是Bridge")}
}func main() {var (f Fishb Bridge)ShowTime(f) // 原先是FishShowTime(b) // 原先是Bridge
}