在C ++中将类分成单独的文件

Question

编辑：添加了“添加”类，意外忘记了它。 如何将类分成不同的文件？我理解类如何工作以及如何制作这样的对象和事物。但是，我发现在将类放入不同文件的过程中存在一些混淆。非常感谢您的帮助！此外，我使用CodeBlocks作为IDE。到目前为止，我的理解是这样的：

1. 创建新课程，CB会为您提供“.h”和新的“.cpp”。
2. 源文件开头的“Classname :: Classname”是范围解析运算符。
3. 您在主源文件中使用“#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。它工作正常，我想我很自豪它:)我知道有更简单的方法来制作这样的东西，但我使用类和对象而不是为了练习的唯一目的。这是我的计算器代码。另外，我真的为长篇帖子道歉：/谢谢你，如果你已经读到这么远了，特别感谢你能帮助我一点！

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，我会以你的榜样告诉你：

subtraction.h

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

subtraction.cxx

#include "subtraction.h"

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

multiplication.h

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

multiplication.cxx

#include "multiplication.h"

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

依旧......

main.cxx

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

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

此外，为了简单起见，我没有把它放在这里的代码中，但是请继续并养成确保声明仅包含一次的习惯。在一个大型项目中，如果你不把这些保护措施放在这里，这会非常讨厌。

#ifndef SUBTRACTION_H
#define SUBTRACTION_H

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

Answer 2

这里有类似乔纳森的例子（为了简洁，我没有添加包含警卫，但确实这样做了！），但是删除了一些复制品并添加了一些OO以供您学习。请注意，虽然这肯定不是实际计算器的实现方式，但如果您对它进行充分研究，它将有助于您对C ++有更多的了解。

mathoperation.h：

  //a base class!
class MathOperation
{
public:
  virtual float doit( float x, float y ) const = 0;
};

subrtaction.h：

class Subtraction : public MathOperation
{
public:
  float doit( float x, float y ) const;
};

addition.h：

class Addition : public MathOperation
{
public:
  float doit( float x, float y ) const;
};

subtraction.cpp：

#include "subtraction.h"
float Subtraction::doit( float x, float y ) const { return x - y; }

addition.cpp：

#include "addition.h"
float Subtraction::doit( float x, float y ) const { return x + y; }

main.cpp中：

#include <iostream>
#include <string>
  //yes this saves typing, but there reasons not to use it.. search SO!
using namespace std;

  //this one avoids you having to copy/paste the similar parts
void DoIt( const MathOperation& op, const std::string& opName, const std::string& verb, const std::string& resultName )
{
  cout << "You have chosen " << opName << "!" << endl;

  cout<<"Enter the first number you want to " << verb << ": "<< endl;

    //here you should actually check if the user really types in a number, and not    "blablabla"
    //and off course, put it in a seperate function so you can reuse it for num2
  float num1;
  cin>>num1;

  float num2;
  cout<<"Enter the second number you wat to " << verb << ": "<< endl;
  cin>>num2;

  cout<<"The " << resultName << " is " << op.doit( num1, num2 ) <<endl;
}

int main()
{
int op;
char cont = 'n';

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;

    //see how much shorter this is?
  if( op == 1 )
    DoIt( Addition(), "Addition", "add", "sum" );
  else if (op==2)
    DoIt( Subtraction(), "Subtraction", "subtract", "difference" );
  else
    cout << "Sorry I don't know this number" << endl;

  cout<<"Do you wish to continue? Y/N"<<endl;
  cin>>cont;

} while (cont=='Y'||cont=='y');

cout<<"Thanks for using my program, goodbye!"<<endl;
return 0;
}

Answer 3

以与课程相同的方式命名文件是件好事。在你的情况下，这不是一个好主意，因为你的类很短，但每个类应该有自己的2个文件 - 例如Subtraction.h和Subtraction.cpp。在.h文件中，你应该只放入decaration - 在你的情况下：     class Subtraction { public: float subtract (float , float); }

在.cpp文件中，您应该包含.h文件并放置实现。在你的情况下：

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

另请参阅C++ Header Files, Code Separation和Why have header files and .cpp files in C++?

希望这有点帮助！ ：）

Answer 4

每个文件只有一个公共类是很好的。 按照惯例，filename与classname相同（如果在文件中完成某些定义，则扩展名为.h .hh或.hpp）。

如果你想将不同的类放在不同的文件中，一个简单的文本编辑器将帮助你做到这一点。