CODEWITHSUNDEEP
c++c++17
aaron scott
aaron scott

Reputation: 39

How can I give the proper return type for this function c++?

My professor gives us templates for programs and wants us to fill out the functions to the prototypes that he gives us, but I am having problems with how to properly return this Date function.

This is the Movie class, template, which instantiates a const Date releaseDate;

class Movie 
    { 
     public:

      -->// all of "name(name), releaseDate(Date(yyyy, mm, dd)) {}"  is what I added to the constructor, I think that is the only way I can 
         // properly instantiate Date because he said Date releaseDate must be constant.

         Movie(string & name, int yyyy, int mm, int dd) : name(name), releaseDate(Date(yyyy, mm, dd)) {}; 
         Date & getReleaseDate(); 
         // other? 
         bool operator== (Movie &); 
         Movie & operator++(); 
         friend ostream & operator<<(ostream &, Movie &); 
         friend ostream & operator<<(ostream &, const Movie &); 

     private: 
         Movie(); 
         const Date releaseDate; 
         string name; 
         int rating;
};

and this is the Date class template

class Date 
{ 
     public: 
        Date(int, int, int); 
        //…. 
        // other as appropriate 
        bool operator==(Date &); 
        friend ostream & operator<<(ostream &, const Date &); 

     private: 
        int day, month, year; 
};

Then this is the overloaded << operator for Date that I believe should be correct

ostream & operator << (ostream & os, const Date & dt)
{
    os << dt.month << "/" << dt.day << "/" << dt.year << "\n";
    return os;
}

The only part I am having trouble with for the date, is how I call 

Date & Movie::getReleaseDate()
{
    cout << releaseDate;
    return releaseDate;
}

it isn't giving me any errors for the cout << overloaded function, but since it says that getReleaseDate() must return something, I have to put in the return, but when I try to return releaseDate, it says "return: cannot convert from const Date to Date &" so what do I need to change to make this work? I am a little confused.

Upvotes: 2

Views: 74

Answers (1)

Asteroids With Wings
Asteroids With Wings

Reputation: 17454

Having a const member like releaseDate limits you. Your class is no longer assignable, for example. Typically I would advise keeping your private data members non-const — you can always expose a non-mutable public interface only.

You have to do that regardless. You cannot return a mutable reference to a const thing. Your getReleaseDate() should either return const Date& or Date (a copy).

Now, the function itself may as well be const so that it works on a const Movie.

It also shouldn't perform output; that's not "wrong" but it's unexpected and not what a user of your class would necessarily want. They can always do cout << movie.getReleaseDate() if they want to do that.

Good job on your operator<<.

Try to avoid the word "template" here. I know what you mean, but "template" means something specific in C++ and this isn't it.

Upvotes: 1

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