struct匿名字段和interface，断言

// 定义interface
type Men interface {
SayHi()
Sing(lyrics string)
}

type Human struct {
name string
age int
phone string
} 
type Student struct {
Human //匿名字段
school string
loan 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，Interface Men的值可以是实现了该接口的任一对象。任何对象只要定义了String方法，都可以用Printf输出函数输出，如下：

type Element interface{}
type List [] Element
type Person struct {
name string
age int
} 

//定义了String方法，实现了fmt.Stringer
func (p Person) String() string {
return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)"
} 

func main() {
list := make(List, 3)
list[0] = 1 // an int
list[1] = "Hello" // a string
list[2] = Person{"Dennis", 70}

// Go语言里面有一个语法，可以直接判断某个接口是否是该类型的变量(断言assert interface.(type))

// value, ok = element.(T)
for index, element := range list {
if value, ok := element.(int); ok {
fmt.Printf("list[%d] is an int and its value is %d\n", index, value)
} else if value, ok := element.(string); ok {
fmt.Printf("list[%d] is a string and its value is %s\n", index, value)
} else if value, ok := element.(Person); ok {
fmt.Printf("list[%d] is a Person and its value is %s\n", index, value)
} else {
fmt.Printf("list[%d] is of a different type\n", index)
}
}
}

//另外一种使用switch的用法:

for index, element := range list{
switch value := element.(type) {
case int:
fmt.Printf("list[%d] is an int and its value is %d\n", index,
case string:
fmt.Printf("list[%d] is a string and its value is %s\n", inde
case Person:
fmt.Printf("list[%d] is a Person and its value is %s\n", inde
default:
fmt.Println("list[%d] is of a different type", index)
}
}

//嵌入interface，类似匿名字段

// io.ReadWriter可以使用Reader和Writer中的所有方法
type ReadWriter interface {
Reader
Writer
}