《Head First设计模式》读书笔记（二）

对于观察者模式,PHP通过标准PHP库(SPL)提供了内建的支持，下面用SPL对昨天的观察者模式示例进行修改。

<?php
    class WeatherData implements SplSubject
    {
        private $observers = null;
        private $temperature = 0;
        private $humidity = 0;
        private $pressure = 0;
        public __construct()
        {
            $this->observers = new SplObjectStorage();
        }
        public function getTemperature()
        {
            return $this->temperature;
        }
        public function setTemperature($temp)
        {
            $this->temperature = $temp;
        }    
        public function getHumidity()
        {
            return $this->humidity;
        }
        public function setHumidity($humidity)
        {
            $this->humidity = $humidity;
        }
        public function getPressure()    
        {
            return $this->pressure;
        }
        public function setPressure($pressure)
        {    
            $this->pressure = $pressure;
        }
        public function setMeasurements($temperature, $humidity, $pressure) 
        {
            $this->setTemperature($temperature);
            $this->setHumidity($humidity);
            $this->setPressure($pressure);
            $this->measureChanged();            
        }
        public function measureChanged()
        {
            $this->notify();
        }
        public function attach(SplObserver $observer)
        {
            $this->observers->attach($observer);
        }
        public function detach(SplObserver $observer)
        {
            $this->observers->detach($observer);
        }
        public function notify()
        {
            foreach ($this->observers as $observer) {
                $observer->update($this);
            }
        }
        public function getObservers() 
        {
            return $this->observers;
        }
    }
    abstract class BaseDisplay implements SplObserver
    {
        private $weatherData = null; 
        public function __construct(WeatherData $weatherData = null)
        {
            $this->weatherData = $weatherData;
            if ($weatherData != null) {
                $this->weatherData->attach($this);
            }
        }
        public function update(SplSubject $subject)
        {
            if ($subject === $this->weatherData) {
                $this->realUpdate($subject);
            }
        }
        abstract function realUpdate(WeatherData $weatherData);
    }
    class CurrentConditionDisplay extends BaseDisplay
    {
        private $temperature = 0;
        private $humidity = 0;
        private $pressure = 0;
        function realUpdate(WeatherData $weatherData)    
        {
            $this->temperature = $weatherData->getTemperature();
            $this->humidity = $weatherData->getHumidity();
            $this->pressure = $weatherData->getPressure();
            print("temp: " . $this->temperature . ", humi: " . $this->humidity . ", pressure: " . $this->pressure . "\n");
        }
    }
    class GeneralDisplay extends BaseDisplay
    {
        function realUpdate(WeatherData $weatherData)    
        {
            print("GeneralDisplay\n");
        }
    }
    $weatherData = new WeatherData();
    $display = new CurrentConditionDisplay($weatherData);
    $display2 = new GeneralDisplay($weatherData);
    $weatherData->setMeasurements(20,30,40);
    $weatherData->detach($display2);
    print("after...\n");
    $weatherData->setMeasurements(33,44,55);
?>