设计模式学习_气象站观察者模式

Posted 2021-08-05 Leslie X徐

观察者模式

概述

由一个主题和若干观察者组成
功能:当主题更新数据时,同步更新数据到已订阅的各个观察者那边,并显示.

气象站

主题:

class Subject{
	public:
	virtual void registerObserver(Observer*)=0;
	virtual void removeObserver(Observer*)=0;
	virtual void notifyObservers()=0;
};

观察者:

class Observer{
	public:
	virtual void update(float,float)=0;
};

其他显示组件接口

class DisplayElement{
	public:
	virtual void display()=0;
};

主题气象站实现:

class WeatherData : 
	public Subject
{
	private:
	vector<Observer*> observers;
	float temperature=0;
	float humidity=0;
	
	public:
	WeatherData(){
		
	}
	
	void registerObserver(Observer* o){
		observers.push_back(o);
	}	
	
	void removeObserver(Observer* o){
		vector<Observer*>::iterator it;
		for(it=observers.begin(); it!=observers.end();++it)
		if(*it==o) observers.erase(it);
	}
	
	void notifyObservers(){
		for(auto i : observers){
			Observer* o = i;
			o->update(this->temperature, this->humidity);
		}
	}
	
	void measurementsChanged(){
		notifyObservers();
	}
	
	void setMeasurements(float temp, float hum){
		this->temperature = temp;
		this->humidity = hum;
		measurementsChanged();
	}
};

观察者实现:

class CurrentConditionDisplay :
	public Observer,
	public DisplayElement
{
	private:
	float temperature=0;
	float humidity=0;
	Subject *weatherData=nullptr;
	
	public:
	CurrentConditionDisplay(Subject *weather){
		this->weatherData = weather;
		this->weatherData->registerObserver(this);
	}
	
	void update(float temp, float hum){
		this->temperature = temp;
		this->humidity = hum;
		display();
	}
	
	void display(){
		cout<<"Current Conditions: "<<endl<<
		"temperature: "<<this->temperature <<endl<<
		"humidity: "<<this->humidity<<endl;
	}
	
	void detach(){
		this->weatherData->removeObserver(this);
	}
};

主函数测试:

int main(int argc, char **argv)
{
	WeatherData weatherdata; 
	CurrentConditionDisplay cur1(&weatherdata);
	CurrentConditionDisplay cur2(&weatherdata);
	
	weatherdata.setMeasurements(12.5,23.5);
	cur1.detach();
	weatherdata.setMeasurements(24,27);
	return 0;
}

与DTH11联合测试

/*
 * 气象站.cxx
 * 
 */


#include "Observer.h"
#include "DTH11.h"

int main(int argc, char **argv)
{
	float temp;
	float hum;
	
	wiringPiStart();
	
	WeatherData weatherdata; 
	CurrentConditionDisplay cur1(&weatherdata);

	while(1){
		delay(2000);
		getDTH(&temp,&hum);
		weatherdata.setMeasurements(temp,hum);
	}

	return 0;
}

输出:

Current Conditions: 
temperature: 32.1
humidity: 57
error2
Current Conditions: 
temperature: 143.19
humidity: 64.183
Current Conditions: 
temperature: 32.1
humidity: 56