Erros with lack of default constructors and inheritance

We're dealing with inheritance and we've been asked to remove the default constructors. I've been looking for answers in 3 different books and online and how found nothing really helpful.

Quote:

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GameEvent.cpp: In constructor ‘GameEvent::GameEvent(Time)’:
GameEvent.cpp:14: error: type ‘Time’ is not a direct base of ‘GameEvent’
GameEvent.cpp:14: error: no matching function for call to ‘Time::Time()’
Time.h:20: note: candidates are: Time::Time(int, int, double)
Time.h:13: note: Time::Time(const Time&)

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GameEvent.h

Code:

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#ifndef GAMEEVENT_H
#define GAMEEVENT_H

#include <string>

using namespace std;

#include "Time.h"
#include "Game.h"

class GameEvent {
protected:
        Time time;
public:
        //        GameEvent();
        GameEvent(const Time t);
        Time getTime();
        const virtual string toString() = 0;
};

#endif /*GAMEEVENT_H*/

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Time.cpp

Code:

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#ifndef TIME_H
#define TIME_H

#include <string>

using namespace std;

class Time {
private:
        int period;
        double seconds;

public:
        /* Time(); */
        Time(int p, int m, double s);
       
        double difference(const Time& other) const;
       
        bool operator<(Time& other);
       
        const string toString();
       
        bool operator==(Time& other);
        static const int NORMAL_SECONDS = 60*15; //Fifteen minutes
        static const int OVERTIME_SECONDS = 60*5; //Five minutes
};

ostream& operator<<(ostream& out, Time& other);

#endif /*TIME_H*/

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well, default constructors are constructors that YOU do not write, i.e. the compiler writes them for you.

So, to remove default constructors, you must write your own. hope that helps

what we had was something like:

Code:

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Time(){} and GameEvent(){}

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We were asked to remove these, and once we did we started getting those errors.

Yes, your base class has a non-trivial constructor (a constructor that takes more one argument or more), so the compiler cannot know which constructor to call or which arguments to pass in.
Here's where you come in. You need to tell the compiler by adding ": ConstructorName(args)" after the constructors in your derived class. Basically it tells the compiler which constructor in the base class to call and what arugments to pass.

Quote:

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Originally Posted by smasherprog

well, default constructors are constructors that YOU do not write, i.e. the compiler writes them for you.

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This is not true. Default constructors are constructors that can be invoked with no arguments. What you are referring to are implicitly declared default constructors.

Quote:

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Originally Posted by Elysia

Yes, your base class has a non-trivial constructor (a constructor that takes more one argument or more), so the compiler cannot know which constructor to call or which arguments to pass in.

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To elaborate: by default, a constructor for a class will invoke the default constructors of the non-static member variables and base classes. However, the Time class has a non-default constructor, thus it does not have an implicitly declared default constructor. As such, you either have to declare the default constructor, or since you were told not to do so, you have to use the constructor initialisation list as Elysia described.