观察者模式是一种行为设计模式，当对象的状态改变时，它允许某些对象通知其他对象。这通常被用于实现事件处理系统。下面我们通过一个简单的天气监控系统来演示在Go语言中如何实现观察者模式。
首先，我们定义Observer（观察者）和Subject（主题）接口：
代码语言：javascript复制type Observer interface {
Update(temperature float64, humidity float64, pressure float64)
}
type Subject interface {
RegisterObserver(o Observer)
RemoveObserver(o Observer)
NotifyObservers()
}
然后，我们创建一个实现了Subject接口的WeatherData结构：
代码语言：javascript复制type WeatherData struct {
observers []Observer
temperature float64
humidity float64
pressure float64
}
func NewWeatherData() *WeatherData {
return &WeatherData{}
}
func (w *WeatherData) RegisterObserver(o Observer) {
w.observers = append(w.observers, o)
}
func (w *WeatherData) RemoveObserver(o Observer) {
for i, observer := range w.observers {
if observer == o {
w.observers = append(w.observers[:i], w.observers[i 1:]...)
}
}
}
func (w *WeatherData) NotifyObservers() {
for _, observer := range w.observers {
observer.Update(w.temperature, w.humidity, w.pressure)
}
}
func (w *WeatherData) measurementsChanged() {
w.NotifyObservers()
}
func (w *WeatherData) SetMeasurements(temperature float64, humidity float64, pressure float64) {
w.temperature = temperature
w.humidity = humidity
w.pressure = pressure
w.measurementsChanged()
}
接下来，我们创建一个实现了Observer接口的CurrentConditionsDisplay结构：
代码语言：javascript复制type CurrentConditionsDisplay struct {
temperature float64
humidity float64
weatherData Subject
}
func NewCurrentConditionsDisplay(weatherData Subject) *CurrentConditionsDisplay {
c := &CurrentConditionsDisplay{weatherData: weatherData}
weatherData.RegisterObserver(c)
return c
}
func (c *CurrentConditionsDisplay) Update(temperature float64, humidity float64, pressure float64) {
c.temperature = temperature
c.humidity = humidity
c.Display()
}
func (c *CurrentConditionsDisplay) Display() {
fmt.Printf("Current conditions: %.2f F degrees and %.2f humidityn", c.temperature, c.humidity)
}
最后，我们的客户端代码看起来像这样：
代码语言：javascript复制func main() {
weatherData := NewWeatherData()
NewCurrentConditionsDisplay(weatherData)
weatherData.SetMeasurements(80, 65, 30.4)
weatherData.SetMeasurements(82, 70, 29.2)
weatherData.SetMeasurements(78, 90, 29.2)
}
运行这段代码，你会看到随着WeatherData的数据更新，CurrentConditionsDisplay的显示也相应的更新了。这就是观察者模式的应用，希望你能从中找到它的价值。
