类和对象-2

#ifndef GRADEBOOK_H
#define GRADEBOOK_H

// GradeBook.h
// GradeBook类展示了该类的公共接口。成员函数出现在GradeBook.cpp中

#include<string>    // 该程序使用C++标准的string类
using std::string;

// GradeBook类的定义
class GradeBook
{
    public:
        /** 构造函数初始化GradeBook对象 */
        GradeBook( string );
        /** Access courseName
         * 返回courseName
         */
        string getCourseName();
        /** Set courseName
         * 设定courseName的值
         */
        void setCourseName(string );
        void displayMessage();  // 显示一条欢迎信息
        void determineClassAverage();   // 计算用户输入的成绩的平均分
    private:
        string courseName; //这个GradeBook的课程名称
};      // GradeBook类定义结尾

#endif // GRADEBOOK_H

// GradeBook.cpp
// Implementation of the GradeBook member-function definitions.
// The setCourseName function performs validation

#include<iostream>
using std::cout;
using std::endl;
using std::cin;

#include "GradeBook.h"  // include definition of class GradeBook

// constructor initializes courseName with string supplied as argument
GradeBook::GradeBook( string name )
{
    setCourseName( name );  // validate and store courseName
}   // end GradeBook constructor

// function that sets the course name
// ensures that the courseName has at most 25 characters
void GradeBook::setCourseName( string name )
{
    if( name.length() <= 25 )   // if name has 25 or fewer characters
        courseName = name;  // store the courseName
    if( name.length() > 25 )    // if name has more than 25 characters
    {
        courseName = name.substr( 0, 25 );  // start at 0, length of 25
        cout << "Name \"" << name << "\" exceeds maximum length (25).\n"
        << "Limiting courseName to the first 25 characters.\n" << endl;
    }

}   // 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 the getCourseName to get the coureName
    cout << "Welcome to the grade book for\n" << getCourseName()
    << "!" << endl;
}   // end function displayMessage

// determine class average based on 10 grades entered by user
void GradeBook::determineClassAverage()
{
    int total;  // sum of grades entered by user
    int gradeCounter;   // number of the grade to be entered next
    int grade;  // grade value entered by user
    int average;    // average of grades

    // initialization phase
    total = 0;  // initialize sum
    gradeCounter = 1;   // initialize loop counter

    // processing phase
    while( gradeCounter <= 10 ) // loop 10 times
    {
        cout << "Enter grade: ";    // prompt for input
        cin >> grade;   // input next grade
        total += grade; // add grade to total
        gradeCounter++; // increment counter by 1
    }   // end while

    // termination phase
    average = total / 10;   // integer division yields integer result

    // display total and average of grades
    cout << "\nTotal of all 10 grades is " << total << endl;
    cout << "Class average is " << average << endl;
}   // end function determineClassAverage

// main.cpp
// Create GradeBook object and invoke its determineClassAverage function.

#include "GradeBook.h"  // include definition of class GradeBook

// function main begins program execution
int main()
{
    // Create GradeBook object myGradeBook and
    // pass course name to constructor

    GradeBook myGradeBook( "CS101 C++ Programming!" );

    myGradeBook.displayMessage();   // display welcome message
    myGradeBook.determineClassAverage();    // find average of 10 grades

    return 0;   // indicate successful termination
}   // end main