抽象类练习（c++ primer plus）

最新推荐文章于 2024-06-22 10:52:50 发布

keepingdo

最新推荐文章于 2024-06-22 10:52:50 发布

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分类专栏： c/cpp 文章标签： c++ os class delete null blog

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本文通过修改《C++ Primer Plus》中的练习题，展示了如何使用基类数组指针和派生类实现多态行为。代码实现了不同派生类的view()方法，用于展示数据。

今晚看《c++ primer plus》做的练习题，呵呵，做的不怎么好，希望高手如果有时间指点一二，谢谢诶！《c++ primer plus》p475练习题3；修改 basedma—lacksdma—hasdma类，让他们都从一个基类派生出来，实现和程序单13.10一样的基本功能，注意使用基类数组指针，在类中添加view（）方法显示数据

代码如下：在vs2005中编译通过！

//filename:dma_abc.h

//定义类，声明类的方法

// // #pragma once #ifndef DMA_ABC_H_ #define DMA_ABC_H_ #include<iostream> namespace kp{ //////////////////////////virtual base class dma//////////////////////// class Dma{ private: char *label; int rating; protected: const char *returnlabel()const{return label;} int returnrating()const{return rating;} public: Dma(const char *l="null",int r=0); Dma(const Dma &dma); virtual ~Dma(); Dma &operator=(const Dma &dma); virtual void View()const =0 ; friend std::ostream &operator<<(std::ostream &os,const Dma &dma); }; ////////////////////////////class basedma :public dma/////////////////////////// class BaseDma:public Dma{ public: BaseDma(const char *l="null",int r=0):Dma(l,r){} BaseDma(const BaseDma &bd):Dma(bd){} //BaseDma&operator=(const BaseDma &bd); virtual void View()const ; friend std::ostream &operator<<(std::ostream &os,const BaseDma &bd); }; ////////////////////////////class lacksdma:public dma//////////////////////////// class LacksDma:public Dma{ private: enum{COL_LEN=40}; char color[COL_LEN]; public: LacksDma(const char *c="black",const char *l="null",int r=0); LacksDma(const char *c,const Dma &Dma); virtual void View()const ; friend std::ostream &operator<<(std::ostream &os,const LacksDma &ld); }; ////////////////////////class hasdma:public dma///////////////////////// class HasDma:public Dma{ private: char *style; public: HasDma(const char *s="none",char *l="null",int r=0); HasDma(const char *s,const Dma &dma); HasDma(const HasDma &hd); virtual ~HasDma(); virtual void View()const; HasDma &operator=(const HasDma &hd); friend std::ostream&operator<<(std::ostream &os,const HasDma &hd); }; } #endif

//filename:dma_abc.cpp

//类方法的实现（定义）

#include<iostream>
#include<cstring>
#include"dma_abc.h"

namespace kp{
    ////////////////////virtual base class dma methods/////////////////
    Dma::Dma(const char *l,int r)
    {
	label=new char[std::strlen(l)+1];
	std::strcpy(label,l);
	rating=r;
    }
    Dma::Dma(const Dma &dma)
    {
	label=new char[std::strlen(dma.label)+1];
	std::strcpy(label,dma.label);
	rating=dma.rating;
    }
     Dma::~Dma()
    {
	delete []label;
    }
     Dma &Dma::operator=(const Dma &dma)
    {
	if (this==&dma)
	    return *this;
	delete []label;
	label=new char[std::strlen(dma.label)+1];
	std::strcpy(label,dma.label);
	rating=dma.rating;
	return *this;
    }
    std::ostream &operator<<(std::ostream &os,const Dma &dma)
    {
	os<<"label: "<<dma.label<<std::endl;
	os<<"rate: "<<dma.rating<<std::endl;
	return os;
    }

/////////////////////////class basedma:public dma methods////////////////
    void BaseDma::View()const
    {
	std::cout<<"label: "<<returnlabel()<<std::endl;
	std::cout<<"rate: "<<returnrating()<<std::endl;
    }
    std::ostream &operator<<(std::ostream &os,const BaseDma &bd)
    {
	os<<(const Dma&)bd;
	return os;
    }
    ////////////////////////////////class lacksdma:public dma methods//////////////////
    LacksDma::LacksDma(const char *c,const char *l,int r):Dma(l,r)
    {
	std::strncpy(color,c,COL_LEN-1);
	color[COL_LEN-1]='/0';
    }
    LacksDma::LacksDma(const char *c,const Dma &dma):Dma(dma)
    {
	std::strncpy(color,c,COL_LEN-1);
	color[COL_LEN-1]='/0';
    }
    void LacksDma::View()const
    {
	std::cout<<"label: "<<returnlabel()<<std::endl;
	std::cout<<"rate: "<<returnrating()<<std::endl;
	std::cout<<"color: "<<color<<std::endl;;
    }
    std::ostream&operator<<(std::ostream &os,const LacksDma &ld)
    {
	os<<(const Dma&)ld;
	os<<"color: "<<ld.color;
	return os;
    }
    ////////////////////////////////////class hasdma:public dma methods///////////
    HasDma::HasDma(const char *s,char *l,int r):Dma(l,r)
    {
	style=new char[std::strlen(s)+1];
	std::strcpy(style,s);
    }
    HasDma::HasDma(const char *s,const Dma&dma):Dma(dma)
    {
	style=new char[std::strlen(s)+1];
	std::strcpy(style,s);
    }
    HasDma::~HasDma()
    {
	delete []style;
    }
    HasDma::HasDma(const HasDma &hd):Dma(hd)
    {
	style=new char[std::strlen(hd.style)+1];
	std::strcpy(style,hd.style);
    }
    void HasDma::View()const
    {
	std::cout<<"label: "<<returnlabel()<<std::endl;
	std::cout<<"rate: "<<returnrating()<<std::endl;
	std::cout<<"style: "<<style<<std::endl;
    }
    HasDma & HasDma::operator =(const HasDma &hd)
    {
	if (this==&hd)
	    return *this;
	Dma::operator =(hd);
	style=new char[std::strlen(hd.style)+1];
	std::strcpy(style,hd.style);
	return *this;
    }
    std::ostream&operator<<(std::ostream  &os,const HasDma &hd)
    {
	os<<(const Dma&)hd;
	os<<"style: "<<hd.style<<std::endl;
	return os;
    }
}

//finename:dma_abcmain.cpp
//主函数，用来测试类

// // #include<iostream> #include"dma_abc.h" int main(int argv,char **argc) { using std::cout; using std::endl; using kp::Dma; using kp::HasDma; using kp::LacksDma; using kp::BaseDma; Dma *p[6]; p[0]=new BaseDma("portablely",8); p[1]=new LacksDma ("red","blimpo",4); p[2]=new HasDma("mercator","buffalo",5); /*cout<<*p[0]<<endl; cout<<*p[1]<<endl; cout<<*p[2]<<endl;*/ p[4]=p[1]; p[3]=new BaseDma(); p[5] =p[3]; /* cout<<*p[3]<<endl; cout<<*p[4]<<endl; cout<<*p[5];*/ for (int i=0;i<6;i++) p[i]->View(); for (int i=0;i<4;i++) delete p[i]; return 0; }

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