在 C++ 中将类分离到单独的文件中

Question

编辑：添加了“加法”类，不小心忘记了。如何将类分成不同的文件？我了解类的工作原理以及如何制作对象和类似的东西。但是，我在将类放入不同文件的过程中发现了一些混乱。非常感谢您的帮助！另外，我使用 CodeBlocks 作为 IDE。到目前为止，这是我的理解：

1. 创建新的类，CB 会给你一个“.h”和一个新的“.cpp”。
2. 源文件开头的“Classname::Classname”是作用域解析运算符。
3. 您可以在主源文件中使用“#include classname.h”来导入其内容。
4. 您可以使用已声明的对象从“main”调用函数。

到目前为止，这是我的理解，但我只是对如何实现它感到困惑。我创建了一个简单的计算器，其中包含一个源文件中的所有类。它工作得很好，我想我为此感到非常自豪:) 我知道有很多更简单的方法来制作这样的东西，但我使用类和对象来代替练习的唯一目的。这是我的计算器代码。另外，我真的为这篇长篇文章道歉：/谢谢，如果你读了这么远，特别感谢你能帮我一点！

这是我在一个源文件中的代码：

#include <iostream>
using namespace std;

class Addition {
public:
float add (float x, float y) {
float sum;
sum=x+y;
return sum;
}


};


class Subtraction {
public:
float subtract (float x, float y) {
float dif;
dif=x-y;
return dif;
}

};

class Multiplication {
public:
float multiply (float x, float y) {
float prod;
prod=x*y;
return prod;
}

};

class Division {
public:
float divide (float x, float y) {
float quot;
quot=x/y;
return quot;
}
};

int op;
char cont;

int main()
{

do {
cout<<"Welcome to C++ Calculator v2!"<<endl;
cout<<"Select the number for which operation you want to use: "<<endl;
cout<<"1-Addition"<<endl;
cout<<"2-Subtraction"<<endl;
cout<<"3-Mutliplication"<<endl;
cout<<"4-Division"<<endl;
cin>>op;

if (op==1) {
float num1;
float num2;
Addition addobj;
cout<<"You have chosen Addition!"<<endl;
cout<<"Enter the first number you want to add: "<<endl;
cin>>num1;
cout<<"Enter the second number you wat to add: "<<endl;
cin>>num2;
float ans=addobj.add(num1, num2);
cout<<"The sum is "<<ans<<endl;
cout<<"Do you wish to continue? Y/N"<<endl;
cin>>cont;
}

if (op==2) {
float num1;
float num2;
Subtraction subobj;
cout<<"You have chosen Subtraction!"<<endl;
cout<<"Enter the first number you want to subtract: "<<endl;
cin>>num1;
cout<<"Enter the second number you want to subtract: "<<endl;
cin>>num2;
float ans=subobj.subtract(num1, num2);
cout<<"The difference is "<<ans<<endl;
cout<<"Do you wish to continue? Y/N"<<endl;
cin>>cont;
}

if (op==3) {
float num1;
float num2;
Multiplication multobj;
cout<<"You have chosen Multiplication!"<<endl;
cout<<"Enter the first number you want to multiply: "<<endl;
cin>>num1;
cout<<"Enter the second number you want to multiply: "<<endl;
cin>>num2;
float ans=multobj.multiply(num1, num2);
cout<<"The product is "<<ans<<endl;
cout<<"Do you wish to continue? Y/N"<<endl;
cin>>cont;
}

if (op==4) {
float num1;
float num2;
Division divobj;
cout<<"You have chosen Division!"<<endl;
cout<<"Enter the first number you want to divide: "<<endl;
cin>>num1;
cout<<"Enter the second number you want to divide: "<<endl;
cin>>num2;
float ans=divobj.divide(num1, num2);
cout<<"The quotient is "<<ans<<endl;
cout<<"Do you wish to continue? Y/N"<<endl;
cin>>cont;
}

} while (cont=='Y'||cont=='y');
if (cont=='N'||'n') {
cout<<"Thanks for using my program, goodbye!"<<endl;
}


return 0;

}

Answer 1

好的，我将通过您的示例向您展示：

减法.h

class Subtraction 
{
public:
 float subtract (float x, float y);
};

减法.cxx

#include "subtraction.h"

float Subtraction::subtract (float x, float y)
{     
  float dif;
  dif=x-y;
  return dif;    
}

乘法.h

class Multiplication 
{
public:
  float multiply (float x, float y);
};

乘法.cxx

#include "multiplication.h"

float Multiplication::multiply (float x, float y)
{
  float prod;
  prod=x*y;
  return prod;
}

等等...

主文件

#include "subtraction.h"
#include "multiplication.h"

int main()
{
 //use the classes just as before.
}

此外，为了简单起见，我没有将它放在此处的代码中，但是继续并养成确保您的声明只包含一次的习惯。在大型项目中，如果您不采取这些保护措施，这会变得非常糟糕。

#ifndef SUBTRACTION_H
#define SUBTRACTION_H

class Subtraction
{
     ....
};
#endif /*SUBTRACTION_H*/