c++ - 默认构造函数错误，没有用于调用的匹配函数

Question

在main()中，我正在创建一个数组myAppointments，并意识到要使其工作，我需要在Appointments.h中创建一个默认构造函数，但是当我这样做时，会出现此错误:

no matching function for call to 'Time::Time()'Appointment(){

Here is Main:

/*
 * Homework 4  -- UPDATE as needed
*/ 
    
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
    
#include "Appointment.h"
using namespace std;
    
void callPrint (Time &TimeOrApptObject) { TimeOrApptObject.print(); }

int main(){
    int month, day, year, hour, minute,howLong;
    Appointment  myAppointments[19];
    
    ifstream HW4DataFileHandle;
    
    HW4DataFileHandle.open("Lab6Data.txt");
    while (!HW4DataFileHandle.eof( )) {
        for (int i = 1; i < 20; i++) {
            HW4DataFileHandle>>month;
            HW4DataFileHandle>>day;
            HW4DataFileHandle>>year;
            HW4DataFileHandle>>hour;
            HW4DataFileHandle>>minute;
            HW4DataFileHandle>>howLong;
            myAppointments[i] = Appointment( month, day, year, hour, minute, howLong);
        }
        cout <<"enter a month" <<endl;
        cin >> month;
        cout <<"enter a day" <<endl;
        cin >> day;
        cout <<"enter a year"<<endl;
        cin >> year;
        Date myDate( month, day, year);
    
        cout <<"Appointments for" << month <<"/" << day <<"/" << year <<":"<< endl;
    
        for (int i = 0; i <13; i++){
            if ( myAppointments[i]==Date myDate )
            {
                Time thisTime = myAppointments[i];
                thisDate.print();
                cout << endl;
            } 
        }
    }

这是头文件:
日期

// Date.h -- Class Date    UPDATE  as needed
#ifndef DATE_H
#define DATE_H

class Date  {  
private:
    int month;
    int day;
    int year;
public:
    Date(int m, int d, int y) : month(m), day(d), year(y)
    {
    }

    friend bool friendTorCompare2Dates (const Date&,const Date& );
};

bool friendTorCompare2Dates (const Date& Right, const Date& Left)
{
    if (Right.month == Left.month && Right.day == Left.day )
        return true;
    else
        return false;
}
    
#endif

时间

//Time.h -- Class Time UPDATE  as needed
using namespace std;
#include<iostream>
#ifndef TIME_H
#define TIME_H

class Time {
private :
    int hour; int minute;
public:
    Time(int h, int m) : hour(h)
    {
    }
    virtual void print() {
        cout << hour << " " << minute <<" "  ;
    }
};

#endif

预约时间

// Appointment.h -- Class Appointment   UPDATE as needed
//
    
using namespace std;
#include "Time.h"
#include "Date.h"
#ifndef APPOINTMENT_H
#define APPOINTMENT_H

class Appointment:  public Date, public Time {  
private:
    int howLong;
public:
    Appointment(int month, int day, int year, int hour, int minute, int howLong) : 
        Date(month, day, year), Time(hour, minute), howLong(howLong)
    {
    }

    Appointment(){
        month;
        day;
        year;
        hour;
        minute;
        howLong;    
    }
};
        
#endif

为了使 Appointment中的默认构造函数正常工作，我需要更改什么？如果您发现其他任何问题，或者对我的问题有任何其他疑问，请告诉我。如果您在回答中加入一个例子，我将不胜感激。

Answer 1

这行:

Appointment  myAppointments[19];

将为每个元素调用 Appointment的默认构造函数。
您的默认构造函数不会显式调用 Time的构造函数，因此将调用 Time的默认构造函数，该构造函数不存在。与 Date相同。
您可以像这样恢复默认构造函数:

class Time {
 // ...
 public:
  Time() = default;
};

为了获得合理的默认行为，您应该为类的成员提供默认的初始值，例如

class Time {
 private :
   int hour = 0; 
   int minute = 0;
public:
   // ...
};