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问题:

解答:
main.cpp

#include <iostream>
#include <string>
#include "dma.h"
using namespace std;
const int CLIENTS = 4;

int main()
{
	ABC* p_clients[CLIENTS];
	char kind;
	for (int i = 0; i < CLIENTS; i++)
	{
		cout << "Select 1)ABC, 2)baseDMA, 3)lacksDMA, 4)hasDMA:";
		while (cin>>kind&&(kind!='1'&&kind!='2'&&kind!='3'&&kind!='4'))
		{
			cout << "Enter either 1 2 3 4 or 4:";
		}
		if (kind == '1')
		{
			p_clients[i] = new ABC();
		}
		else if (kind == '2')
		{
			while (cin.get() != '\n')continue;
			char l[40];
			int r;
			cout << "Enter baseDMA's label:";
			cin.getline(l, 40);
			cout << "Enter baseDMA's rating:";
			cin >> r;
			p_clients[i] = new baseDMA(l, r);
		}
		else if (kind == '3')
		{
			while (cin.get() != '\n')continue;
			char  l[40], c[40];
			int r;
			cout << "Enter lacksDMA's label:";
			cin.getline(l, 40);
			cout << "Enter lacksDMA's color:";
			cin.getline(c, 40);
			cout << "Enter lacksDMA's rating:";
			cin >> r;
			p_clients[i] = new lacksDMA(c, l, r);
		}
		else if (kind == '4')
		{
			while (cin.get() != '\n')continue;
			char  l[40], s[40];
			int r;
			cout << "Enter hassDMA's label:";
			cin.getline(l, 40);
			cout << "Enter hasDMA's style:";
			cin.getline(s, 40);
			cout << "Enter hasDMA's rating:";
			cin >> r;
			p_clients[i] = new hasDMA(s, l, r);
		}
		while (cin.get()!='\n')
		{
			continue;
		}
	}
	cout << endl;

	for (int i = 0; i < CLIENTS; i++)
	{
		p_clients[i]->View();
		cout << endl;
	}
	for (int i = 0; i < CLIENTS; i++)
	{
		delete p_clients[i];
	}
	cout << "DONE" << endl;

	return 0;
}

dma.h

#pragma once
#include <iostream>
using namespace std;

class ABC
{
public:
	virtual ~ABC(){};
	virtual void View() { cout << "This is ABC View(),it is empty.\n"; }
};

class baseDMA:public ABC
{
private:
	char* label;
	int rating;

public:
	baseDMA(const char* l = "null", int r = 0);
	baseDMA(const baseDMA& rs);
	virtual ~baseDMA();
	virtual void View()override;
	baseDMA& operator=(const baseDMA& rs);
	friend ostream& operator<<(ostream& os, const baseDMA& rs);
};

class lacksDMA :public baseDMA
{
private:
	enum{COL_LEN=40};
	char color[COL_LEN];
public:
	lacksDMA(const char* c = "blank", const char* l = "nnull", int r = 0);
	lacksDMA(const char* c, const baseDMA& rs);
	virtual void View()override;
	friend ostream& operator<<(ostream& os, const lacksDMA& ls);
};

class hasDMA :public baseDMA
{
private:
	char* style;
public:
	hasDMA(const char* s = "none", const char* l = "null",int r=0);
	hasDMA(const char* s, const baseDMA& rs);
	hasDMA(const hasDMA& hs);
	~hasDMA();
	virtual void View()override;
	hasDMA& operator=(const hasDMA& hs);
	friend ostream& operator<<(ostream& os, const hasDMA& hs);
};

dma.cpp

#include "dma.h"

baseDMA::baseDMA(const char* l, int r)
{
	label = new char[strlen(l) + 1];
	strcpy_s(label, strlen(l) + 1,l);
	rating = r;
}
baseDMA::baseDMA(const baseDMA& rs)
{
	label = new char[strlen(rs.label) + 1];
	strcpy_s(label, strlen(rs.label) + 1, rs.label);
	rating = rs.rating;
}
baseDMA::~baseDMA()
{
	delete[] label;
}
void baseDMA::View()
{
	cout << "Now in baseDMA" << endl;
	cout << *this << endl;
}
baseDMA& baseDMA::operator=(const baseDMA& rs)
{
	if (this == &rs)return *this;
	if (label)delete[] label;
	label = new char[strlen(rs.label) + 1];
	strcpy_s(label, strlen(rs.label) + 1, rs.label);
	rating = rs.rating;
	return *this;
}
ostream& operator<<(ostream& os, const baseDMA& rs)
{
	os << "label: " << rs.label << "\trating:" << rs.rating;
	return os;
}


lacksDMA::lacksDMA(const char* c, const char* l , int r ):baseDMA(l,r)
{
	strcpy_s(color, COL_LEN, c);
	if (strlen(c) >= COL_LEN)color[COL_LEN - 1] = '\0';
	else color[strlen(c)] = '\0';
}
lacksDMA::lacksDMA(const char* c, const baseDMA& rs) :baseDMA(rs)
{
	strcpy_s(color, COL_LEN, c);
	if (strlen(c) >= COL_LEN)color[COL_LEN - 1] = '\0';
	else color[strlen(c)] = '\0';
}
void lacksDMA::View()
{
	cout << "Now in lacksDMA." << endl;
	cout << *this << endl;
}
ostream& operator<<(ostream& os, const lacksDMA& ls)
{
	os << (const baseDMA&)ls;
	os << "\tColor:" << ls.color;
	return os;
}


hasDMA::hasDMA(const char* s, const char* l, int r):baseDMA(l,r)
{
	style = new char[strlen(s) + 1];
	strcpy_s(style, strlen(s) + 1, s);
}
hasDMA::hasDMA(const char* s, const baseDMA& rs):baseDMA(rs)
{
	style = new char[strlen(s) + 1];
	strcpy_s(style, strlen(s) + 1, s);
}
hasDMA::hasDMA(const hasDMA& hs):baseDMA(hs)
{
	style = new char[strlen(hs.style) + 1];
	strcpy_s(style, strlen(hs.style) + 1, hs.style);
}
hasDMA::~hasDMA()
{
	delete[] style;
}
void hasDMA::View()
{
	cout << "Now in hasDMA." << endl;
	cout << *this << endl;
}
hasDMA& hasDMA::operator=(const hasDMA& hs)
{
	if (this == &hs)return *this;
	baseDMA::operator=(hs);
	delete[]style;
	style = new char[strlen(hs.style) + 1];
	strcpy_s(style, strlen(hs.style) + 1, hs.style);
	return *this;
}
ostream& operator<<(ostream& os, const hasDMA& hs)
{
	os << (const baseDMA&)hs;
	os << "\tStyle:" << hs.style;
	return os;
}

运行结果:

考查点:

• 继承
• 多态

注意:

• 父类的函数参数可以传子类
  

2024年9月9日15:14:58