heatindexdisplay.hpp

深入浅出设计模式（书配套c++源代码)。包含20个设计模式的c++实现。

#ifndef	_HFDP_CPP_OBSERVER_HEAT_INDEX_DISPLAY_HPP_	
#define _HFDP_CPP_OBSERVER_HEAT_INDEX_DISPLAY_HPP_

#include "WeatherStation.hpp"

namespace HeadFirstDesignPatterns {
namespace Observer {

class HeatIndexDisplay : private Observer, private DisplayElement {

	private: Subject* _weatherData;
	private: float _heatIndex;

	private: HeatIndexDisplay( const HeatIndexDisplay& ); // Disable copy constructor
	private: void operator=( const HeatIndexDisplay& ); // Disable assignment operator

	public: explicit HeatIndexDisplay( Subject* weatherData ) :
		_weatherData( weatherData ), _heatIndex( 0.0 ) { assert( weatherData );
		_weatherData->registerObserver( this );
	}
	public: ~HeatIndexDisplay() {
		_weatherData->removeObserver( this );
	}
	public: void update( float t, float rh, float pressure ) {
		_heatIndex = computeHeatIndex( t, rh );
		display();
	}
	private: float computeHeatIndex( float t, float rh ) const {
		float index = (float)((16.923 + (0.185212 * t) + (5.37941 * rh) - (0.100254 * t * rh) 
			+ (0.00941695 * (t * t) ) + (0.00728898 * (rh * rh) ) 
			+ (0.000345372 * (t * t * rh) ) - (0.000814971 * (t * rh * rh) ) +
			(0.0000102102 * (t * t * rh * rh) ) - (0.000038646 * (t * t * t) ) + (0.0000291583 * 
			(rh * rh * rh) ) + (0.00000142721 * (t * t * t * rh) ) + 
			(0.000000197483 * (t * rh * rh * rh) ) - (0.0000000218429 * (t * t * t * rh * rh) ) +
			0.000000000843296 * (t * t * rh * rh * rh) ) -
			(0.0000000000481975 * (t * t * t * rh * rh * rh) ) );
		return index;
	}
	public: void display() const {
		std::cout.setf( std::ios::showpoint);
		std::cout.precision(7);
		std::cout << "Heat index is " << _heatIndex << std::endl;
	}
};

} // namespace Observer
} // namespace HeadFirstDesignPatterns

#endif