C++: Pure Virtual Functions 

  1 #include <iostream>
  2 #include <string>
  3 using namespace std;
  4 
  5 #define DEBUGBUILD 0
  6 #define DEBUG if (DEBUGBUILD) cout
  7 
  8 class Date{
  9 private:
 10     int day, month, year;
 11 public:
 12     Date(){ DEBUG << "Date: default ctor" << endl;}
 13     Date(int m, int d, int y) {
 14         DEBUG << "Date: 3 int ctor" << endl;
 15         day=d;
 16         month=m;
 17         year=y;
 18     }
 19     void Display(void) { cout << month << "/" << day << "/" << year << endl;}
 20 };
 21 
 22 class Time {
 23 private:
 24     int hour, minute, second;
 25 public:
 26     Time(){    DEBUG << "Time: default ctor" << endl;}
 27     Time(int h, int m, int s)    {
 28         DEBUG << "Time: 3 int ctor" << endl;
 29         hour=h;
 30         minute=m;
 31         second=s;
 32     }
 33     void Display(){    cout << hour << ":" << minute << ":" << second << endl; }
 34 };
 35 
 36 class Document { // abstract class
 37 public:
 38     virtual void Display() = 0; // pure virtual function
 39 };
 40 
 41 class Report : public Document {
 42 private:
 43     Date repDate;
 44     Time repTime;
 45     string repDesc;
 46 public:
 47     Report() : repDate(1,1,1970), repTime(0,0,0), repDesc("")
 48     {
 49         DEBUG << "Report: default ctor" << endl;
 50         repDesc = "";
 51     }
 52     Report(Date d, Time t, string desc) : repDate(d), repTime(t)
 53     {
 54         DEBUG << "Report: date time string ctor" << endl;
 55         repDesc = desc;
 56     }
 57     virtual void Display()
 58     {
 59         cout << "Date: ";
 60         repDate.Display();
 61         cout << "Time: ";
 62         repTime.Display();
 63         cout << "Description: ";
 64         DisplayDesc();
 65     }
 66     void DisplayDesc() { cout << repDesc << endl; }
 67 };
 68 
 69 class GradeReport : public Report {
 70 private:
 71     int StudentID;
 72     int CourseID;
 73 public:
 74     GradeReport() : StudentID(0), CourseID(0)
 75     { DEBUG << "GradeReport: default ctor" << endl; }
 76 
 77     GradeReport(Date d, Time t, string desc, int sid, int cid) : 
 78     Report(d, t, desc), StudentID(sid), CourseID(cid)
 79     { DEBUG << "GradeReport: 5 parameters ctor" << endl; }
 80 
 81     GradeReport(const GradeReport& gr) : 
 82     Report(gr), StudentID(gr.StudentID), CourseID(gr.CourseID)
 83     { DEBUG << "GradeReport: Copy ctor" << endl; }
 84 
 85     ~GradeReport() { DEBUG << "GradeReport: dtor" << endl; }
 86 
 87     virtual void Display() {
 88         DisplayID();
 89         cout << "Course ID: " << CourseID << endl;
 90         Report::Display();
 91     }
 92     void DisplayID() { cout << "Student ID: " << StudentID << endl; }
 93 };
 94 
 95 class Counselor : public Document {
 96 private:
 97     Date counseledDate;
 98     string counselorName;
 99     GradeReport* badGrade;
100 public:
101     Counselor() { DEBUG << "Counselor: default ctor" << endl; }
102 
103     ~Counselor() { DEBUG << "Counselor: dtor" << endl;    }
104 
105     Counselor(const Counselor &cr) : counseledDate(cr.counseledDate), 
106         badGrade(cr.badGrade),
107         counselorName(cr.counselorName)
108     { DEBUG << "Counselor: copy ctor" << endl; }
109 
110     Counselor(Date d, string name, GradeReport *gptr) : counseledDate(d), badGrade(gptr),
111         counselorName(name)
112     {     DEBUG << "Counselor: Date, string, GradeReport* ctor" << endl; }
113 
114     virtual void Display() {
115         cout << "Student ";
116         badGrade->DisplayID();
117         cout << "Counseled on: ";
118         counseledDate.Display();
119         cout << "Counselor's name: " << counselorName << endl;
120     }
121 };
122 
123 void ShowReport(Document* doc){
124     cout << "*********************************" << endl;
125     doc->Display();
126     cout << "*********************************" << endl;
127 }
128 
129 void main()
130 {
131     Date today(6, 4, 2011);
132     Time t(8, 0, 0);
133     GradeReport gradeA(today, t, "CS360", 1234, 100);
134 
135     Date today2(7, 4, 2011);
136     Time t2(18, 0, 0);
137     Report status(today2, t2, "July Report");
138 
139     Date counseled(10, 18, 2011);
140     Counselor helper(counseled, "Paul Davis", &gradeA);
141 
142     Document *doc[3];
143     doc[0] = &gradeA;
144     doc[1] = &status;
145     doc[2] = &helper;
146 
147     for(int i = 0; i < 3; i++)
148         ShowReport(doc[i]);
149 }

posted @ 2011-06-28 10:15  Mayus  阅读(235)  评论(0)    收藏  举报