go 内嵌对象类型

demo1

// Sample program to show how to embed a type into another type and
// the relationship between the inner and outer type.
package main

import (
    "fmt"
)

// user defines a user in the program.
type user struct {
    name  string
    email string
}

// notify implements a method that can be called via
// a value of type user.
func (u *user) notify() {
    fmt.Printf("Sending user email to %s<%s>\n",
        u.name,
        u.email)
}

// admin represents an admin user with privileges.
type admin struct {
    user  // Embedded Type
    level string
}

// main is the entry point for the application.
func main() {
    // Create an admin user.
    ad := admin{
        user: user{
            name:  "john smith",
            email: "[e-mail]",
        },
        level: "super",
    }

    // We can access the inner type's method directly.
    ad.user.notify()

    // The inner type's method is promoted.
    ad.notify()
}

输出

Sending user email to john smith<[e-mail]>
Sending user email to john smith<[e-mail]>

demo2

// Sample program to show how to embed a type into another type and
// the relationship between the inner and outer type.
package main

import (
    "fmt"
)

// user defines a user in the program.
type user struct {
    name  string
    email string
}

// notify implements a method that can be called via
// a value of type user.
func (u *user) notify() {
    fmt.Printf("Sending user email to %s<%s>\n",
        u.name,
        u.email)
}

// admin represents an admin user with privileges.
type admin struct {
    user  // Embedded Type
    level string
}

func (u *admin) notify() {
    fmt.Printf("admin method!\n")
}

// main is the entry point for the application.
func main() {
    // Create an admin user.
    ad := admin{
        user: user{
            name:  "john smith",
            email: "[e-mail]",
        },
        level: "super",
    }

    // We can access the inner type's method directly.
    ad.user.notify()

    // The inner type's method is promoted.
    ad.notify()
}

输出

Sending user email to john smith<[e-mail]>
admin method!

demo3

// Sample program to show how embedded types work with interfaces.
package main

import (
    "fmt"
)

// notifier is an interface that defined notification
// type behavior.
type notifier interface {
    notify()
}

// user defines a user in the program.
type user struct {
    name  string
    email string
}

// notify implements a method that can be called via
// a value of type user.
func (u *user) notify() {
    fmt.Printf("Sending user email to %s<%s>\n",
        u.name,
        u.email)
}

// admin represents an admin user with privileges.
type admin struct {
    user
    level string
}

// main is the entry point for the application.
func main() {
    // Create an admin user.
    ad := admin{
        user: user{
            name:  "john smith",
            email: "[e-mail]",
        },
        level: "super",
    }

    // Send the admin user a notification.
    // The embedded inner type's implementation of the
    // interface is "promoted" to the outer type.
    sendNotification(&ad)
}

// sendNotification accepts values that implement the notifier
// interface and sends notifications.
func sendNotification(n notifier) {
    n.notify()
}

输出

Sending user email to john smith<[e-mail]>