C++构造函数

#include <iostream>
#include <string>
using namespace std;
class GradeBook
{
public:
   // constructor initializes courseName with string supplied as argument
   // 构造函数  用于这个类被创建时要做的事情
   GradeBook( string name ,int money )
   {
      setCourseName( name ); // call set function to initialize courseName
      setCourseMoney(money);
   } // end GradeBook constructor

   // function to set the course name
   void setCourseName( string name )
   {
      courseName = name; // store the course name in the object
   } // end function setCourseName

   // function to get the course name
   string getCourseName()
   {
      return courseName; // return object's courseName
   } // end function getCourseName

   // display a welcome message to the GradeBook user
   void displayMessage()
   {
      // call getCourseName to get the courseName
      cout << "Welcome to the grade book for\n" << getCourseName()  
         << "!" << endl;
   } // end function displayMessage
   void setCourseMoney(int money){
       courseMoney = money;
   }
   int getCourseMoney(){
       return courseMoney;
   }
private:
   string courseName;
   int courseMoney;
};

// function main begins program execution
int main()
{
   // create two GradeBook objects
   GradeBook gradeBook1( "C++", 1000 );
   GradeBook gradeBook2( "Python" , 2000);

   // display initial value of courseName for each GradeBook
   cout << "gradeBook1 created for course: " << gradeBook1.getCourseName()
      << "\ngradeBook2 created for course: " << gradeBook2.getCourseName() 
      << endl;

//   gradeBook1.setCourseMoney(1000);

    cout << "gradeBook1 CourseMoney: " << gradeBook1.getCourseMoney() << endl;;
    cout << "gradeBook2 CourseMoney: " << gradeBook2.getCourseMoney() << endl;;
}

### 包含用户定义类的头文件

编写GradeBook.h头文件

#include <iostream>
#include <string> // class GradeBook uses C++ standard string class
using namespace std;

class GradeBook
{
public:
   // constructor initializes courseName with string supplied as argument
   GradeBook( string name )
   {
      setCourseName( name ); // call set function to initialize courseName
   } // end GradeBook constructor

   // function to set the course name
   void setCourseName( string name )
   {
      courseName = name; // store the course name in the object
   } // end function setCourseName

   // function to get the course name
   string getCourseName()
   {
      return courseName; // return object's courseName
   } // end function getCourseName

   // display a welcome message to the GradeBook user
   void displayMessage()
   {
      // call getCourseName to get the courseName
      cout << "Welcome to the grade book for\n" << getCourseName()  
         << "!" << endl;
   } // end function displayMessage
private:
   string courseName; // course name for this GradeBook
}; // end class GradeBook  

编写测试cpp文件

注意引入 #include “GradeBook.h”

#include <iostream>
#include "GradeBook.h"

using namespace std;

int main()
{
   // create two GradeBook objects
   GradeBook gradeBook1( "CS101 Introduction to C++ Programming" );
   GradeBook gradeBook2( "CS102 Data Structures in C++" );

   // display initial value of courseName for each GradeBook
   cout << "gradeBook1 created for course: " << gradeBook1.getCourseName()
      << "\ngradeBook2 created for course: " << gradeBook2.getCourseName() 
      << endl;
} // end main

接口与实现分离

接口的作用：只做声明， 不做实现
编写接口 GradeBook.h

#include <string> // class GradeBook uses C++ standard string class
using namespace std;

// GradeBook class definition
class GradeBook
{
public:
   GradeBook( string ); // constructor that initializes courseName
   void setCourseName( string ); // function that sets the course name
   string getCourseName(); // function that gets the course name
   void displayMessage(); // function that displays a welcome message
private:
   string courseName; // course name for this GradeBook
}; // end class GradeBook  

实现类：做具体的实现

#include <iostream>
#include "GradeBook.h" // include definition of class GradeBook
using namespace std;

// constructor initializes courseName with string supplied as argument
GradeBook::GradeBook( string name )
{
   setCourseName( name ); // call set function to initialize courseName
} // end GradeBook constructor

// function to set the course name
void GradeBook::setCourseName( string name )
{
   courseName = name; // store the course name in the object
} // end function setCourseName

// function to get the course name
string GradeBook::getCourseName()
{
   return courseName; // return object's courseName
} // end function getCourseName

// display a welcome message to the GradeBook user
void GradeBook::displayMessage()
{
   // call getCourseName to get the courseName
   cout << "Welcome to the grade book for\n" << getCourseName() 
      << "!" << endl;
} // end function displayMessage

`

测试类将接口include即可

// Fig. 3.13: fig03_13.cpp
// GradeBook class demonstration after separating 
// its interface from its implementation.
#include <iostream>
#include "GradeBook.h" // include definition of class GradeBook
using namespace std;

// function main begins program execution
int main()
{
   // create two GradeBook objects
   GradeBook gradeBook1( "CS101 Introduction to C++ Programming" );
   GradeBook gradeBook2( "CS102 Data Structures in C++" );

   // display initial value of courseName for each GradeBook
   cout << "gradeBook1 created for course: " << gradeBook1.getCourseName()
      << "\ngradeBook2 created for course: " << gradeBook2.getCourseName() 
      << endl;
} // end main