Just for fun——go实现一下观察者模式

代码

package main

import (
    "fmt"
)

type Subject interface {
    RegisterObserver(o Observer)
    RemoveObserver(o Observer)
    NotifyAllObservers()
}

type Observer interface {
    // 温度,湿度,气压
    Update(temp float32, humidity float32, pressure float32)
}

type WeatherData struct {
    Temperature float32
    Humidity    float32
    Pressure    float32
    Observers   map[Observer]bool
}

func NewWeathData() *WeatherData {
    return &WeatherData{
        Observers: make(map[Observer]bool),
    }
}

func (wd *WeatherData) RegisterObserver(o Observer) {
    wd.Observers[o] = true
}

func (wd *WeatherData) RemoveObserver(o Observer) {
    if _, ok := wd.Observers[o]; ok {
        delete(wd.Observers, o)
    }
}

func (wd *WeatherData) NotifyAllObservers() {
    for o, _ := range wd.Observers {
        o.Update(wd.Temperature, wd.Humidity, wd.Pressure)
    }
}

func (wd *WeatherData) SetMeasurements(temp float32, humidity float32, pressure float32) {
    wd.Temperature = temp
    wd.Humidity = humidity
    wd.Pressure = pressure
    wd.NotifyAllObservers()
}

type CurrentConditionsDisplay struct {
    Temperature float32
    Humidity    float32
    weathData   Subject
}

func NewCurrentConditionsDisplay(weathData Subject) *CurrentConditionsDisplay {
    ccd := &CurrentConditionsDisplay{
        weathData: weathData,
    }
    weathData.RegisterObserver(ccd)
    return ccd
}

func (ccd *CurrentConditionsDisplay) Update(temp float32, humidity float32, pressure float32) {
    ccd.Temperature = temp
    ccd.Humidity = humidity
    // pressure 没用到
    ccd.Display()
}

func (ccd *CurrentConditionsDisplay) Display() {
    fmt.Println("Current conditions: " + fmt.Sprintf("%v", ccd.Temperature) + "F degrees and " + fmt.Sprintf("%v", ccd.Humidity) + "% humidity")
}

func main() {
    weathData := NewWeathData()

    _ = NewCurrentConditionsDisplay(weathData)
    weathData.SetMeasurements(80, 65, 30.4)
    weathData.SetMeasurements(82, 70, 29.2)
    weathData.SetMeasurements(78, 90, 29.2)
}

测试

输出

Current conditions: 80F degrees and 65% humidity
Current conditions: 82F degrees and 70% humidity
Current conditions: 78F degrees and 90% humidity