如何使用Golang实现观察者模式_对象状态变化通知多个观察者

// Observer 是一个接受更新数据的函数类型
type Observer func(data interface{})

// Subject 管理观察者并触发通知
type Subject struct {
    observers []Observer
    mu        sync.RWMutex
}

func (s *Subject) Register(obs Observer) {
    s.mu.Lock()
    defer s.mu.Unlock()
    s.observers = append(s.observers, obs)
}

func (s *Subject) Unregister(obs Observer) {
    s.mu.Lock()
    defer s.mu.Unlock()
    for i, o := range s.observers {
        if o == obs {
            s.observers = append(s.observers[:i], s.observers[i+1:]...)
            break
        }
    }
}

func (s *Subject) Notify(data interface{}) {
    s.mu.RLock()
    defer s.mu.RUnlock()
    for _, obs := range s.observers {
        obs(data) // 异步通知？可另起 goroutine，但需注意并发安全
    }
}

type TemperatureSensor struct {
    *Subject
    temperature float64
}

func NewTemperatureSensor() *TemperatureSensor {
    return &TemperatureSensor{
        Subject: &Subject{observers: make([]Observer, 0)},
    }
}

func (t *TemperatureSensor) SetTemperature(temp float64) {
    t.temperature = temp
    t.Notify(map[string]float64{"temperature": temp})
}

func (t *TemperatureSensor) GetTemperature() float64 {
    return t.temperature
}

sensor := NewTemperatureSensor()

// 日志观察者
sensor.Register(func(data interface{}) {
    fmt.Println("LOG: sensor updated →", data)
})

// 告警观察者
sensor.Register(func(data interface{}) {
    if v, ok := data.(map[string]float64); ok {
        if t := v["temperature"]; t > 80.0 {
            fmt.Println("ALERT: High temperature detected!", t)
        }
    }
})

// 触发变更
sensor.SetTemperature(85.5) // 同时输出 log 和 alert

func (s *Subject) NotifyAsync(data interface{}) {
    s.mu.RLock()
    obsCopy := append([]Observer(nil), s.observers...) // 安全拷贝
    s.mu.RUnlock()

    var wg sync.WaitGroup
    for _, obs := range obsCopy {
        wg.Add(1)
        go func(o Observer) {
            defer wg.Done()
            o(data)
        }(obs)
    }
    wg.Wait()
}