访问者模式.cpp

#include <iostream>
#include <list>
#include <memory>
using namespace std;// 提供一个作用于某对象结构中的各元素的操作表示，便可以在不改变各元素类的前提下定义（扩展）作用于这些元素的新操作
// 允许一个或多个操作应用于一组对象上，使对象本身和操作解耦
// 5种角色
// Visitor（抽象访问者），为对象结构中的元素声明访问接口
// ConcreteVisitor（具体访问者），实现接口
// Element（抽象元素），定义Accept方法，形参通常为Visitor指针
// ConcreteElement（具体元素），实现Accept方法，该方法中调用ConcreteVisitor的访问操作，实现元素操作
// ObjectStructure（对象结构），元素集合，存放元素对象并提供遍历其内部元素的接口，一般用于同一批元素的相同操作namespace ns1
{class Medicine // 药品父类{public:virtual ~Medicine() {}virtual string getMdcName() const = 0; // 药品名称virtual float getPrice() const = 0;    // 药品总价格，单位：元};class M_asplcrp : public Medicine // 药品：阿司匹林肠溶片{public:string getMdcName() const override{return "Aspirin enteric-coated tablets";}float getPrice() const override{return 46.8f; // 为简化代码，直接给出药品总价而不单独强调药品数量了，比如该药品医生给开了两盒，一盒是23.4，那么这里直接返回两盒的价格}};class M_fftdnhsp : public Medicine // 药品：氟伐他汀钠缓释片{public:string getMdcName() const override{return "Fluvastatin sodium sustained-release tablets";}float getPrice() const override{return 111.3f; // 三盒的价格}};class M_dlx : public Medicine // 药品：黛力新{public:string getMdcName() const override{return "Deanxit";}float getPrice() const override{return 122.0f; // 两盒的价格}};class MedicineProc // 针对药品的处理相关类{list<shared_ptr<Medicine>> m_mdclist; // 药品列表，记录着药品单上的所有药品public:// 增加药品到药品列表中void addMedicine(const shared_ptr<Medicine> &p_mdc) { m_mdclist.push_back(p_mdc); }// 针对费用缴纳和取药所做的处理动作void procAction(const string &strvisitor) // strvisitor代表拿到了药品单的人，不同的人拿到药品单所要做的处理也不同{if (strvisitor == "Toll collector") // 收费人员要根据药品单向我（患者）收取费用{float totalcost = 0.0f; // 总费用for (auto iter = m_mdclist.begin(); iter != m_mdclist.end(); ++iter){float tmpprice = (*iter)->getPrice();totalcost += tmpprice;cout << "yao: " << (*iter)->getMdcName() << ", price: " << tmpprice << endl;}cout << "total price: " << totalcost << ", Toll collector charges a fee!" << endl;}else if (strvisitor == "Drug taking personnel") // 取药人员要根据药品单为我拿药for (auto iter = m_mdclist.begin(); iter != m_mdclist.end(); ++iter)cout << "Drug taking personnel give " << (*iter)->getMdcName() << " to me!" << endl;else if (strvisitor == "dietitian")cout << "Nutritionist suggested: match coarse grains with staple foods and eat meat properly!" << endl;else if (strvisitor == "Fitness coach")cout << "The fitness coach suggested: do more aerobic exercises such as jogging (35 minutes), warm up before and after jogging, avoid anxiety, avoid staying up late, and take a bed rest before 22:30!" << endl;}};
}namespace ns2
{class Visitor; // 类前向声明class Medicine // 药品父类{public:virtual ~Medicine() {}virtual void Accept(shared_ptr<Visitor> &pvisitor) = 0; // 这里的形参是访问者父类指针public:virtual string getMdcName() = 0; // 药品名称virtual float getPrice() = 0;    // 药品总价格，单位：元};class M_asplcrp : public Medicine // 药品：阿司匹林肠溶片{public:string getMdcName() override { return "Aspirin enteric-coated tablets"; }float getPrice() override { return 46.8f; }public:void Accept(shared_ptr<Visitor> &pvisitor) override;};class M_fftdnhsp : public Medicine // 药品：氟伐他汀钠缓释片{public:string getMdcName() override { return "Fluvastatin sodium sustained-release tablets"; }float getPrice() override { return 111.3f; }public:void Accept(shared_ptr<Visitor> &pvisitor) override;};class M_dlx : public Medicine // 药品：黛力新{public:string getMdcName() override { return "Deanxit"; }float getPrice() override { return 122.0f; }public:void Accept(shared_ptr<Visitor> &pvisitor) override;};class Visitor // 访问者父类{public:virtual ~Visitor() {}virtual void Visit_elm_asplcrp(M_asplcrp *pelem) = 0;   // 访问元素：阿司匹林肠溶片virtual void Visit_elm_fftdnhsp(M_fftdnhsp *pelem) = 0; // 访问元素：氟伐他汀钠缓释片virtual void Visit_elm_dlx(M_dlx *pelem) = 0;           // 访问元素：黛力新以下几个接口的名字都叫Visit（成员函数重载）// virtual void Visit(M_asplcrp* pelem) = 0;   //访问元素：阿司匹林肠溶片// virtual void Visit(M_fftdnhsp* pelem) = 0;  //访问元素：氟伐他汀钠缓释片// virtual void Visit(M_dlx* pelem) = 0;       //访问元素：黛力新};class Visitor_SFRY : public Visitor // 收费人员访问者子类{float m_totalcost = 0.0f; // 总费用public:void Visit_elm_asplcrp(M_asplcrp *pelem) override{float tmpprice = pelem->getPrice();cout << "yao: " << pelem->getMdcName() << ", price: " << tmpprice << endl;m_totalcost += tmpprice;}void Visit_elm_fftdnhsp(M_fftdnhsp *pelem) override{float tmpprice = pelem->getPrice();cout << "yao: " << pelem->getMdcName() << ", price: " << tmpprice << endl;m_totalcost += tmpprice;}void Visit_elm_dlx(M_dlx *pelem) override{float tmpprice = pelem->getPrice();cout << "yao: " << pelem->getMdcName() << ", price: " << tmpprice << endl;m_totalcost += tmpprice;}// 返回总费用float getTotalCost() const { return m_totalcost; }};class Visitor_QYRY : public Visitor // 取药人员访问者子类{public:void Visit_elm_asplcrp(M_asplcrp *pelem) override{cout << "Drug taking personnel give " << pelem->getMdcName() << " to me!" << endl;}void Visit_elm_fftdnhsp(M_fftdnhsp *pelem) override{cout << "Drug taking personnel give " << pelem->getMdcName() << " to me!" << endl;}void Visit_elm_dlx(M_dlx *pelem) override{cout << "Drug taking personnel give " << pelem->getMdcName() << " to me!" << endl;}};class Visitor_YYS : public Visitor // 营养师访问者子类{public:void Visit_elm_asplcrp(M_asplcrp *pelem) override{cout << "The nutritionist suggested: Eating more coarse grains and less oil can effectively prevent blood clots!" << endl;}void Visit_elm_fftdnhsp(M_fftdnhsp *pelem) override{cout << "The nutritionist suggested: Eating more mushrooms, onions, and kiwifruit can effectively reduce blood lipids!" << endl;}void Visit_elm_dlx(M_dlx *pelem) override{cout << "The nutritionist suggested: Go out more to breathe fresh air, get more sunshine, go to more crowded places, and keep an optimistic and cheerful mood!" << endl;}};// 各个药品子类Accept方法的实现体代码void M_asplcrp::Accept(shared_ptr<Visitor> &pvisitor){pvisitor->Visit_elm_asplcrp(this);}void M_fftdnhsp::Accept(shared_ptr<Visitor> &pvisitor){pvisitor->Visit_elm_fftdnhsp(this);}void M_dlx::Accept(shared_ptr<Visitor> &pvisitor){pvisitor->Visit_elm_dlx(this);}class ObjectStructure // 对象结构{list<shared_ptr<Medicine>> m_mdclist; // 药品列表public:// 增加药品到药品列表中void addMedicine(const shared_ptr<Medicine> &p_mdc){m_mdclist.push_back(p_mdc);}void procAction(shared_ptr<Visitor> &pvisitor){for (auto iter = m_mdclist.begin(); iter != m_mdclist.end(); ++iter)(*iter)->Accept(pvisitor);}};
}namespace ns3
{class Medicine; // 类前向声明class Visitor   // 访问者父类{public:virtual ~Visitor() {}virtual void Visit(Medicine *const pelem) = 0;};class Medicine // 药品父类{public:virtual ~Medicine() {}virtual void Accept(shared_ptr<Visitor> &pvisitor) { pvisitor->Visit(this); }public:virtual string getMdcName() const = 0; // 药品名称virtual float getPrice() const = 0;    // 药品总价格，单位：元};class M_asplcrp : public Medicine // 药品：阿司匹林肠溶片{public:string getMdcName() const override { return "Aspirin enteric-coated tablets"; }float getPrice() const override { return 46.8f; }};class M_fftdnhsp : public Medicine // 药品：氟伐他汀钠缓释片{public:string getMdcName() const override { return "Fluvastatin sodium sustained-release tablets"; }float getPrice() const override { return 111.3f; }};class M_dlx : public Medicine // 药品：黛力新{public:string getMdcName() const override { return "Deanxit"; }float getPrice() const override { return 122.0f; }};class Visitor_SFRY : public Visitor // 收费人员访问者子类{float m_totalcost = 0.0f; // 总费用public:void Visit(Medicine *const m) override{float tmpprice = m->getPrice();m_totalcost += tmpprice;cout << "yao: " << m->getMdcName() << ", price: " << tmpprice << endl;}float getTotalCost() const { return m_totalcost; } // 返回总费用};class Visitor_QYRY : public Visitor // 取药人员访问者子类{public:void Visit(Medicine *const m) override{cout << "Drug taking personnel give " << m->getMdcName() << " to me!" << endl;}};class Visitor_YYS : public Visitor // 营养师访问者子类{public:void Visit(Medicine *const m) override{cout << "The nutritionist suggested: Eating more coarse grains and less oil can effectively prevent blood clots!" << endl;cout << "The nutritionist suggested: Eating more mushrooms, onions, and kiwifruit can effectively reduce blood lipids!" << endl;cout << "The nutritionist suggested: Go out more to breathe fresh air, get more sunshine, go to more crowded places, and keep an optimistic and cheerful mood!" << endl;}};class ObjectStructure // 对象结构{list<shared_ptr<Medicine>> m_mdclist; // 药品列表public:// 增加药品到药品列表中void addMedicine(const shared_ptr<Medicine> &p_mdc){m_mdclist.push_back(p_mdc);}void procAction(shared_ptr<Visitor> &pvisitor){for (auto iter = m_mdclist.begin(); iter != m_mdclist.end(); ++iter)(*iter)->Accept(pvisitor);}};
}int main()
{
#if 0using namespace ns1;shared_ptr<Medicine> pm1(new M_asplcrp());  // 药品阿司匹林肠溶片shared_ptr<Medicine> pm2(new M_fftdnhsp()); // 药品氟伐他汀钠缓释片shared_ptr<Medicine> pm3(new M_dlx());      // 药品黛力新MedicineProc mdcprocobj;mdcprocobj.addMedicine(pm1);mdcprocobj.addMedicine(pm2);mdcprocobj.addMedicine(pm3);mdcprocobj.procAction("Toll collector");mdcprocobj.procAction("Drug taking personnel");
#endif#if 1// using namespace ns2;using namespace ns3;shared_ptr<Medicine> mdc_asplcrp(new M_asplcrp());shared_ptr<Medicine> mdc_fftdnhsp(new M_fftdnhsp());shared_ptr<Medicine> mdc_dlx(new M_dlx());// 各个元素子类调用Accept接受访问者的访问，就可以实现访问者要实现的功能shared_ptr<Visitor> visitor_sf(new Visitor_SFRY()); // 收费人员访问者子类，里面承载着向我（患者）收费的算法mdc_asplcrp->Accept(visitor_sf);                    // 累加“阿司匹林肠溶片”的价格mdc_fftdnhsp->Accept(visitor_sf);                   // 累加“氟伐他汀钠缓释片”的价格mdc_dlx->Accept(visitor_sf);                        // 累加“黛力新”的价格cout << "total price: " << dynamic_pointer_cast<Visitor_SFRY>(visitor_sf)->getTotalCost() << ", the toll collector charged me!" << endl;shared_ptr<Visitor> visitor_qy(new Visitor_QYRY()); // 取药人员访问者子类，里面承载着向我发放药品的算法mdc_asplcrp->Accept(visitor_qy);                    // 我取得“阿司匹林肠溶片”mdc_fftdnhsp->Accept(visitor_qy);                   // 我取得“氟伐他汀钠缓释片”mdc_dlx->Accept(visitor_qy);                        // 我取得“黛力新”shared_ptr<Visitor> visitor_yys(new Visitor_YYS()); // 营养师访问者子类，里面承载着为我配置营养餐的算法mdc_asplcrp->Accept(visitor_yys);                   // 营养师针对治疗预防血栓药“阿司匹林肠溶片”给出的对应的营养餐建议mdc_fftdnhsp->Accept(visitor_yys);                  // 营养师针对降血脂药“氟伐他汀钠缓释片”给出的对应的营养餐建议mdc_dlx->Accept(visitor_yys);                       // 营养师针对治疗神经紊乱药“黛力新”给出的对应的营养餐建议shared_ptr<ObjectStructure> objstruc(new ObjectStructure());objstruc->addMedicine(mdc_asplcrp);objstruc->addMedicine(mdc_fftdnhsp);objstruc->addMedicine(mdc_dlx);objstruc->procAction(visitor_yys); // 将一个访问者对象（visitor_yys）应用到一批元素上，以实现对一批元素进行同一种（营养方面的）操作
#endifcout << "Over!\n";return 0;
}