test_interface.go

package main

import "fmt"

type User struct {
	Name string
	Age  int
}

// func (u *User) GetName() string {
// 	return u.Name
// }

func (u *User) GetAge() int {
	return u.Age
}

type Named interface {
	GetName() string
}

type Aged interface {
	GetAge() int
}

func main() {
	u1 := &User{Name: "John", Age: 32}
	var i interface{} = u1

	aged, ok := i.(Aged)
	if ok {
		fmt.Printf("age: %d\n", aged.GetAge())

		named, ok := aged.(Named)
		if ok {
			fmt.Printf("name: %s\n", named.GetName())
		}
	}
}