observer CurrentConditionsDisplay

observer/app.d

@@ -0,0 +1,14 @@
+module observer.app;
+
+import observer.weatherdata;
+import observer.currentconditionsdisplay;
+
+void main()
+{
+    WeatherData weatherData = new WeatherData();
+    CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);
+
+    weatherData.setMeasurements(80, 65, 30.4f);
+    weatherData.setMeasurements(82, 70, 29.2f);
+    weatherData.setMeasurements(78, 90, 29.2f);
+}

observer/currentconditionsdisplay.d

@@ -0,0 +1,31 @@
+module observer.currentconditionsdisplay;
+import observer.displayelement;
+import observer.observer;
+import observer.weatherdata;
+import std.stdio : writeln;
+import std.format : format;
+
+class CurrentConditionsDisplay : Observer, DisplayElement
+{
+private:
+    float temperature;
+    float humidity;
+    WeatherData weatherData;
+public:
+    this(WeatherData weatherData)
+    {
+        weatherData.registerObserver(this);
+    }
+
+    override void update(float temperature, float humidity, float pressure)
+    {
+        this.temperature = temperature;
+        this.humidity = humidity;
+        display();
+    }
+
+    override void display()
+    {
+        writeln("Current conditions: %3.1f".format(temperature), "F degrees and %3.1f%% humidity".format(humidity));
+    }
+}

observer/displayelement.d

@@ -0,0 +1,6 @@
+module observer.displayelement;
+
+interface DisplayElement
+{
+    void display();
+}

observer/observer.d

@@ -0,0 +1,6 @@
+module observer.observer;
+
+interface Observer
+{
+    void update(float temp, float humidity, float pressure);
+}

observer/subject.d

@@ -0,0 +1,9 @@
+module observer.subject;
+import observer.observer;
+
+interface Subject
+{
+    void registerObserver(Observer o);
+    void removeObserver(Observer o);
+    void notifyObservers();
+}

observer/weatherdata.d

@@ -1,2 +1,57 @@
 module observer.weatherdata;
+import observer.subject;
+import observer.observer;
+import std.algorithm : remove, countUntil;
 
+class WeatherData : Subject
+{
+private:
+    Observer[] observers;
+    float temperature, humidity, pressure;
+public:
+    override void registerObserver(Observer o)
+    {
+        observers ~= o;
+    }
+    
+    override void removeObserver(Observer o)
+    {
+        observers.remove(observers.countUntil(o));
+    }
+
+    override void notifyObservers()
+    {
+        foreach (Observer o; observers)
+        {
+            o.update(temperature, humidity, pressure);
+        }
+    }
+
+    void measurementsChanged()
+    {
+        notifyObservers();
+    }
+
+    void setMeasurements(float temperature, float humidity, float pressure)
+    {
+        this.temperature = temperature;
+        this.humidity = humidity;
+        this.pressure = pressure;
+        measurementsChanged();
+    }
+
+    @property float getTemperature()
+    {
+        return temperature;
+    }
+
+    @property float getHumidity()
+    {
+        return humidity;
+    }
+
+    @property float getPressure()
+    {
+        return pressure;
+    }
+}