星球狂想战队|一起来学C++：C++中的代码重用( 九 ) 本章内容包括：

下面来看一个例子，并介绍有哪些问题以及如何解决它们。要使用MI ，需要几个类。我们将定义一个抽象基类Worker ，并使用它派生出Waiter类和Singer类。然后，便可以使用MI从Waiter类和Singer类派生出SingingWaiter类（参见图14.3）。这里使用两个独立的派生来使基类（Worker）被继承，这将导致MI的大多数麻烦。首先声明Worker、Waiter和Singer类，如程序清单14.7所示。
程序清单14.7Worker0.h
//worker0.h--workingclasses#ifndefWORKER0_H_#defineWORKER0_H_#includeclassWorker//anabstractbaseclass{private:std::stringfullname;longid;public:Worker():fullname("noone"),id(0L){}Worker(conststd::string&s,longn):fullname(s),id(n){}virtual~Worker()=0;//purevirtualdestructorvirtualvoidSet();virtualvoidShow()const;};classWaiter:publicWorker{private:intpanache;public:Waiter():Worker(),panache(0){}Waiter(conststd::string&s,longn,intp=0):Worker(s,n),panache(p){}Waiter(constWorker&wk,intp=0):Worker(wk),panache(p){}voidSet();voidShow()const;};classSinger:publicWorker{protected:enum{other,alto,contralto,soprano,bass,baritone,tenor};enum{Vtypes=7};private:staticchar*pv[Vtypes];//stringequivsofvoicetypesintvoice;public:Singer():Worker(),voice(other){}Singer(conststd::string&s,longn,intv=other):Worker(s,n),voice(v){}Singer(constWorker&wk,intv=other):Worker(wk),voice(v){}voidSet();voidShow()const;};#endif程序清单14.7的类声明中包含一些表示声音类型的内部常量。一个枚举用符号常量alto、contralto等表示声音类型，静态数组pv存储了指向相应C-风格字符串的指针，程序清单14.8初始化了该数组，并提供了方法的定义。
【星球狂想战队|一起来学C++：C++中的代码重用】程序清单14.8worker0.cpp
//worker0.cpp--workingclassmethods#include"worker0.h"#includeusingstd::cout;usingstd::cin;usingstd::endl;//Workermethods//mustimplementvirtualdestructor,evenifpureWorker::~Worker(){}voidWorker::Set(){cout<<"Enterworker'sname:";getline(cin,fullname);cout<<"Enterworker'sID:";cin>>id;while(cin.get()!='n')continue;}voidWorker::Show()const{cout<<"Name:"<<fullname<<"n";cout<<"EmployeeID:"<<id<<"n";}//WaitermethodsvoidWaiter::Set(){Worker::Set();cout<<"Enterwaiter'spanacherating:";cin>>panache;while(cin.get()!='n')continue;}voidWaiter::Show()const{cout<<"Category:waitern";Worker::Show();cout<<"Panacherating:"<<panache<<"n";}//Singermethodschar*Singer::pv[]={"other","alto","contralto","soprano","bass","baritone","tenor