[GoF设计模式]Decorator模式和Observer模式的C++实现

【Decorator模式】

Decorator模式提供了一种给类增加职责的方法，不是通过直接继承实现的，而是通过组合，下图中的WorkerDecorator类可以派生很多在Worker基础上扩展出来的类，而不仅仅只是SeniorWorker，可以有不同的扩展。这是装饰者模式的威力所在。

但是如果只是给WorkComponent添加一个修饰，WorkDecorator可以省去，但以后可扩展性就不强了。

注意：基类指针指向派生类时，通过该指针只能访问到基类中所提供的接口。

Decorator采用组合的方式取得了比采用继承的方式更好的效果。

 

【图解】

 普通的工人能够进行粉墙和喷漆的工作，现在需要技术工人，即掌握粉墙和喷漆的能力外，还需要有进行设计的能力。

 

 

【程序】

/******************************************************************* * * DESCRIPTION: WorkerComponent[工人] Class (Component Class in Decorator Pattern) * * AUTHOR:Neesky * * DATE:2009-9-22 * *******************************************************************/ #ifndef WORKERCOMPONENT_H_ #define WORKERCOMPONENT_H_ class WorkerComponent { public: WorkerComponent(){} virtual ~WorkerComponent(){} /*activities of worker*/ virtual void painting()=0;//Worker must can paiting[会喷漆] virtual void brushing()=0;//Worker must can brushing[会刷墙] }; #endif  

/******************************************************************* * * DESCRIPTION: Worker Class [Concreate Component Class in Decorator Pattern] * * AUTHOR:Neesky * * DATE:2009-9-22 * *******************************************************************/ #ifndef WORKER_H_ #define WORKER_H_ /** include files **/ #include <iostream> #include "WorkerComponent.h" using namespace std; class Worker:public WorkerComponent { public: Worker(){} virtual ~Worker(){} /*activities of worker*/ virtual void brushing() { cout<<"Hi,I am a Worker, and I am brushing......"<<endl; return; } virtual void painting() { cout<<"Hi,I am a Worker, and I am painting......"<<endl; return; } }; #endif  

/******************************************************************* * * DESCRIPTION: WorkerDecorator Class, inherited from WorkComponent * * AUTHOR:Neesky * * DATE:2009-9-22 * *******************************************************************/ #ifndef WORKDECORATOR_H_ #define WORKDECORATOR_H_ /** include files **/ #include "WorkerComponent.h" class WorkerDecorator:public WorkerComponent { public: /*constructor and destructor*/ WorkerDecorator(WorkerComponent *workerComponent) { this->_workcomponent=workerComponent; } virtual ~WorkerDecorator() { if(this->_workcomponent!=NULL) delete this->_workcomponent; } /*Inherited from WorkerComponent*/ //virtual void painting()=0; //virtual void brushing()=0; protected:/*Very Important:protected*/ WorkerComponent *_workcomponent;//Key Point to use the Worker's capability }; #endif  

/******************************************************************* * * DESCRIPTION: SeniorWorker[资深工人] ,inherited from WorkerDecorator Class * * AUTHOR:Neesky [Concreate Decorator Class ] * * DATE:2009-9-22 * *******************************************************************/ #ifndef SENIORWORKER_H_ #define SENIORWORKER_H_ /** include files **/ #include "WorkerDecorator.h" class SeniorWorker:public WorkerDecorator { public: /*constuctor and destructor*/ SeniorWorker(WorkerComponent *workerComponent):WorkerDecorator(workerComponent) { } virtual ~SeniorWorker() { if(this->_workcomponent!=NULL)delete this->_workcomponent; } /*activities of worker*/ virtual void brushing() { cout<<"Senior Worker:"<<flush; this->_workcomponent->brushing(); return; } virtual void painting() { cout<<"Senior Worker:"<<flush; this->_workcomponent->painting(); return; } /*Additional Function: activities of senior worker*/ virtual void designing() { cout<<"Senior Worker:Hi，I am a senior worker，and I am designing......"<<endl; return; } }; #endif  

/******************************************************************* * * DESCRIPTION: Main Program [Decorator模式]-装饰者模式 * * AUTHOR:Neesky * * DATE:2009-9-22 * *******************************************************************/ /** include files **/ #include <iostream> #include "Worker.h" #include "WorkerComponent.h" #include "SeniorWorker.h" using namespace std; int main (int argc, char *argv[]) { /*Prototype Pattern*/ WorkerComponent* worker=new Worker(); cout<<"/nNow Here is a worker......"<<endl; worker->brushing();//Brush wall first worker->painting();//Paint later /*SeniorWorker must have capability of worker object*/ SeniorWorker *seniorworker=new SeniorWorker(worker); cout<<"/nNow Here is a senior worker......"<<endl; seniorworker->designing(); seniorworker->brushing(); seniorworker->painting(); return(0); }  

【输出】

 

 

【Observer模式】

Observer模式是应用最多影响最广的模式，MVC就是基于Observer模式的，改模式在系统开发和设计过程中有重要意义，MVC实现了业务层和表示层的解耦。Observer模式也是开发过程中必须要掌握的使用模式之一。

建个一(subject)对多(observer)的关系，当一发生变化的时候，依赖一的多也能同步改变。

【图解】

当温度数据发生变化时，我们期望反应温度数据的柱状图型和曲线图也能同步做出更新。

 

【程序】

/******************************************************************* * * DESCRIPTION: Data Subject Class * * AUTHOR: Neesky * * DATE:2009-9-23 * *******************************************************************/ #ifndef DATASUBJECT_H_ #define DATASUBJECT_H_ /**include files**/ #include <list> using namespace std; #include "DataObserver.h" /*Predeclaration*/ class DataObserver; class DataSubject { public: /*constructor and destructor*/ DataSubject() { this->obList=new list<DataObserver*>; this->Data=0.0; } virtual ~DataSubject() { if(this->obList!=NULL) delete this->obList; } /*Interface Functions*/ virtual void AttachObserver(DataObserver *observer) { this->obList->push_back(observer); return; } virtual void DetachObserver(DataObserver *observer) { list<DataObserver*>::iterator it=std::find(this->obList->begin(), this->obList->end(), observer); if(it!=this->obList->end()) this->obList->erase(it); return; } /*Notify Observers As obList*/ virtual void NotifyObservers_toUpdate() { list<DataObserver*>::iterator iter=obList->begin(); for(;iter!=obList->end();++iter) (*iter)->Update(); return; } /*Get Or Set Data*/ virtual void SetData(double _newData)=0; virtual double GetData()=0; protected: double Data; list<DataObserver*> *obList; }; #endif  

/******************************************************************* * * DESCRIPTION: Temperature Data Class 温度数据类 * * AUTHOR:Neesky * * DATE:2009-9-23 * *******************************************************************/ #ifndef TEMPERATUREDATA_H_ #define TEMPERATUREDATA_H_ /** include files **/ #include "DataSubject.h" class TemperatureData:public DataSubject { public: /*constructor and destructor*/ TemperatureData(){} virtual ~TemperatureData(){} /*implement the interface*/ virtual double GetData() { return this->Data; } virtual void SetData(double _newData) { if(this->Data!=_newData) { this->Data=_newData; this->NotifyObservers_toUpdate();/*Notify Observers*/ } return; } }; #endif  

/******************************************************************* * * DESCRIPTION: Data Observer Class * * AUTHOR:Neesky * * DATE:2009-9-23 * *******************************************************************/ #ifndef DATAOBSERVER_H_ #define DATAOBSERVER_H_ /**include files**/ #include "DataSubject.h" /*Predeclaration*/ class DataSubject; class DataObserver { public: DataObserver(){} virtual ~DataObserver(){} /*Interface Functions*/ virtual void Update()=0; protected: DataSubject *_datasubject; }; #endif  

/******************************************************************* * * DESCRIPTION:Graph Observer Class[数据的曲线图表示] * * AUTHOR: Neesky * * DATE:2009-9-23 * *******************************************************************/ #ifndef GRAPHOBSERVER_H_ #define GRAPHOBSERVER_H_ /** include files **/ #include "DataObserver.h" class GraphObserver:public DataObserver { public: /*constructor and destructor*/ GraphObserver(DataSubject* datasubject) { this->_datasubject=datasubject; this->_datasubject->AttachObserver(this);/*Register: observe*/ } virtual ~GraphObserver() { if(this->_datasubject!=NULL) this->_datasubject->DetachObserver(this);/*Un Register*/ } /*Implement Interface*/ virtual void Update() { this->dataView=this->_datasubject->GetData();/*Updata local data copy*/ return; } /*get method*/ virtual double GetDataView() { return this->dataView; } private: double dataView;/*local data copy*/ }; #endif  

/******************************************************************* * * DESCRIPTION:Histogram Observer Class[数据的曲线图表示] * * AUTHOR: Neesky * * DATE:2009-9-23 * *******************************************************************/ #ifndef HISTOGRAMOBSERVER_H_ #define HISTOGRAMOBSERVER_H_ /** include files **/ #include "DataObserver.h" class HistogramObserver:public DataObserver { public: /*constructor and destructor*/ HistogramObserver(DataSubject *datasubject) { this->_datasubject=datasubject; this->_datasubject->AttachObserver(this);/*Register: observe*/ this->Update(); } virtual ~HistogramObserver() { if(this->_datasubject!=NULL) this->_datasubject->DetachObserver(this);/*Un Register*/ } /*Implement Interface*/ virtual void Update() { this->dataView=this->_datasubject->GetData();/*Updata local data copy*/ return; } /*get method*/ virtual double GetDataView() { return this->dataView; } private: double dataView;/*local data copy*/ }; #endif  

/******************************************************************* * * DESCRIPTION: Observer Patterns [观察者模式] * * AUTHOR:Neesky * * DATE:2009-9-23 * *******************************************************************/ /** include files **/ #include <iostream> using namespace std; #include "TemperatureData.h" #include "GraphObserver.h" #include "HistogramObserver.h" int main (int argc, char *argv[]) { /*Now there is a temperature data*/ DataSubject *temperature=new TemperatureData(); /*Now there are serveral observers*/ GraphObserver *graphForTemperature=new GraphObserver(temperature); HistogramObserver *histogramForTemperature=new HistogramObserver(temperature); /*Now temperature changed to be 37.5 C*/ cout<<"/nNow Temperature is changed to be 37.5 C!"<<endl; temperature->SetData(37.5);/*Call the NotifyObservers_toUpdate, it call Observers' update method*/ /*See Graph's view data if changed*/ cout<<"GraphObserver's temperature dataView is: "<<graphForTemperature->GetDataView()<<endl; cout<<"HistogramObserver's temperature dataView is: "<<histogramForTemperature->GetDataView()<<endl; cout<<"/nNow Detach the GraphObserver......"; temperature->DetachObserver(graphForTemperature); cout<<"Ok"<<endl; /*Now temperature changed to be 37.5 C*/ cout<<"/nNow Temperature is changed to be 40.3 C!"<<endl; temperature->SetData(40.3);/*Call the NotifyObservers_toUpdate, it call Observers' update method*/ /*See Graph's view data if changed*/ cout<<"GraphObserver's temperature dataView is: "<<graphForTemperature->GetDataView()<<endl; cout<<"HistogramObserver's temperature dataView is: "<<histogramForTemperature->GetDataView()<<endl; return(0); }  

 

【输出】