试题六(共 15 分)阅读下列说明和 C++代码,填补代码中的空缺,将解答填入答

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问题 试题六(共 15 分)阅读下列说明和 C++代码,填补代码中的空缺,将解答填入答题纸的对应栏内。【说明】以下 C++代码实现一个简单客户关系管理系统(CrM)中通过工厂(Customerfactory)对象来创建客户(Customer)对象的功能。客户分为创建成功的客户(realCustomer)和空客户(NullCustomer)。空客户对象是当不满足特定条件时创建或获取的对象。类间关系如图6-1 所示。【C++代码】#include<iostream>#include<string>using namespace std; class Customer{protected:string name;public:(1) boll isNil()=0;(2) string getName()=0;﹜; class realCustomer (3){public:realCustomer(string name){this->name=name;﹜bool isNil(){ return false;﹜string getName(){ return name;﹜﹜; class NullCustomer (4) {public:bool isNil(){ return true;﹜string getName(){ return 〝Not Available in Customer Database〞; ﹜﹜;class Customerfactory{public:string names[3]={〝rob〞, 〝Joe〞,〝Julie〞﹜;public:Customer*getCustomer(string name){for (int i=0;i<3;i++){if (names[i].(5) ){return new realCustomer(name);﹜﹜return (6);﹜﹜; class CrM{public:void getCustomer(){Customerfactory*(7);Customer*customer1=cf->getCustomer(〝rob〞);Customer*customer2=cf->getCustomer(〝Bob〞);Customer*customer3=cf->getCustomer(〝Julie〞);Customer*customer4=cf->getCustomer(〝Laura〞); cout<<〝Customers〞<<endl;cout<<Customer1->getName() <<endl; delete  customer1;cout<<Customer2->getName() <<endl; delete customer2;cout<<Customer3->getName() <<endl; delete  customer3;cout<<Customer4->getName() <<endl; delete  customer4;delete cf;﹜﹜; int main(){CrM*crs=new CrM();crs->getCustomer();delete crs;return 0;﹜ /*程序输出为:CustomersrobNot Available in Customer DatabaseJulieNot Available in Customer Database*/

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答案

解析 1)virtual2)virtual3):public Customer4):public Customer5)compare(name)==06)new Null Customer()7)cf=New CustomerFactory();
【解析】

本题考察使用C++代码实现实际问题。在C++中,动态绑定是通过虚函数来实现的。此题中用到了虚函数,所以要在成员函数原型缺钱加一个关键字virtual。类RealCustomer和类NullCustomer是类Customer的派生类,因此3、4空都填public Customer。进行对比数据库中的人名compare(name)==0第6空与前面语句是相反的,一个是返回new RealCustomer(name),那么此处应填:new Null Customer()第7空,用工厂创建对象,cf=New CustomerFactory();
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