Golang Observer事件订阅与通知模式示例

package main

import "fmt"

// Observer 观察者接口
type Observer interface {
    Update(message string)
}

// Subject 主题结构体
type Subject struct {
    observers []Observer
}

// Subscribe 添加观察者
func (s *Subject) Subscribe(o Observer) {
    s.observers = append(s.observers, o)
}

// Unsubscribe 移除观察者
func (s *Subject) Unsubscribe(o Observer) {
    for i, obs := range s.observers {
        if obs == o {
            s.observers = append(s.observers[:i], s.observers[i+1:]...)
            break
        }
    }
}

// Notify 通知所有观察者
func (s *Subject) Notify(message string) {
    for _, observer := range s.observers {
        observer.Update(message)
    }
}

// 具体观察者：邮件服务
type EmailService struct{}

func (e *EmailService) Update(message string) {
    fmt.Println("Email sent:", message)
}

// 具体观察者：日志服务
type LogService struct{}

func (l *LogService) Update(message string) {
    fmt.Println("Log recorded:", message)
}

// 示例使用
func main() {
    subject := &Subject{}
    email := &EmailService{}
    log := &LogService{}

    // 订阅
    subject.Subscribe(email)
    subject.Subscribe(log)

    // 发布事件
    subject.Notify("User registered")

    // 取消订阅
    subject.Unsubscribe(email)

    // 再次通知
    subject.Notify("User logged in")
}

Email sent: User registered
Log recorded: User registered
Log recorded: User logged in