c++中对象，继承的引用

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我是靠谱客的博主温暖钥匙，这篇文章主要介绍c++中对象，继承的引用，现在分享给大家，希望可以做个参考。

在c++中在传递一个父类引用的参数的时候，可以传递一个子类的实参进去，这也是继承中的一些特点，意味着子类可以使用父类的特点

具体例子入下：

复制代码

// TheRefOfc++.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void file_it(ostream& os, double fo, const double fe[], int n);
const int MINIT = 5;
int _tmain(int argc, _TCHAR* argv[])
{
ofstream fout;
const char* fn = "ep-data.txt";
fout.open(fn);
if (!fout.is_open()){
cout << "Can't open " << fn << ".Bye" << endl;
exit(EXIT_FAILURE);
}
double objective;
cout << "Enter the focal length of your teleescope objective in mm: ";
cin >> objective;
double eps[MINIT];
cout << "Enetr the focal lengths , in mm m of " << MINIT << "eyepices:" << endl;
for (int i = 0; i < 5; i++)
{
cout << "Eyepiece :" << i + 1 << ":";
cin >> eps[i];
}
file_it(fout, objective, eps, MINIT);
file_it(fout, objective, eps, MINIT);
cout << "Done!" << endl;
return 0;
}
void file_it(ostream& os, double fo, const double fe[], int n){
ios_base::fmtflags initial;
initial = os.setf(ios_base::fixed);
os.precision(2);
os << "Focal lenght of objective: " << fo << "mm" << endl;
os.setf(ios::showpoint);
os.precision(1);
os.width(12);
os << "f.1 eyepiece ";
os.width(15);
os << "magnification " << endl;
for (int i = 0; i < MINIT; i++)
{
os.width(12);
os << fe[i];
os.width(15);
os << int(fo / fe[i] + 0.5) << endl;
}
}

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// TheRefOfc++.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void file_it(ostream& os, double fo, const double fe[], int n);
const int MINIT = 5;
int _tmain(int argc, _TCHAR* argv[])
{
ofstream fout;
const char* fn = "ep-data.txt";
fout.open(fn);
if (!fout.is_open()){
cout << "Can't open " << fn << ".Bye" << endl;
exit(EXIT_FAILURE);
}
double objective;
cout << "Enter the focal length of your teleescope objective in mm: ";
cin >> objective;
double eps[MINIT];
cout << "Enetr the focal lengths , in mm m of " << MINIT << "eyepices:" << endl;
for (int i = 0; i < 5; i++)
{
cout << "Eyepiece :" << i + 1 << ":";
cin >> eps[i];
}
file_it(fout, objective, eps, MINIT);
file_it(fout, objective, eps, MINIT);
cout << "Done!" << endl;
return 0;
}
void file_it(ostream& os, double fo, const double fe[], int n){
ios_base::fmtflags initial;
initial = os.setf(ios_base::fixed);
os.precision(2);
os << "Focal lenght of objective: " << fo << "mm" << endl;
os.setf(ios::showpoint);
os.precision(1);
os.width(12);
os << "f.1 eyepiece ";
os.width(15);
os << "magnification " << endl;
for (int i = 0; i < MINIT; i++)
{
os.width(12);
os << fe[i];
os.width(15);
os << int(fo / fe[i] + 0.5) << endl;
}
}