Question

Hello I’m wondering why is const used at the “get” functions in this class?

class Album {

public:
    Album(string c, Artist* a, string t, int y, int no):barCode(c), artist(a), title(t), year(y), noCopiesSold(no){}
    const string& getBarCode() const {return barCode;}
    Artist* getArtist() const {return artist;}
    const string& getTitle() const {return title;}
    int getYear() const {return year;}
    int getNoCopiesSold() const {return noCopiesSold;}
    void setBarCode(string value) {barCode = value;}
    void setArtist(Artist* value) {artist = value;}
    void setTitle(string value) {title = value;}
    void setYear(int value) {year = value;}
    void setNoCopiesSold(int value) {noCopiesSold = value;}

    friend ostream& operator << (ostream& out, const Album& album)
    {
        out << album.artist->getName() << " " << album.barCode << " " << album.title << " " << album.year << " " << album.noCopiesSold << endl;
        return out;
    }

private:
    string barCode;
    Artist* artist;
    string title;
    int year;
    int noCopiesSold;
};

Answer 1

why is “const used at the “get” functions in this class?

For const-correctness.

1. By making a function const, it implies that the function is not
   changing any non-static member variable inside it and no other non-const function is called inside
   this method
2. The function now can be called using a const object also (otherwise
   results in compiler error)
3. Many library functions make use of const correct methods; so const-correctness make your method compatible with it (e.g. less than operator — bool <Class>::operator < (const Class&) const)