Question

I was wondering if enumeration is commonly used with user input. I’m doing an exercise in which in my Book class I have to create an enum Genre with different genre enumerators such as fiction, non, fiction etc.

When the user uses the program, he/she is asked for certain information about the book being stored. For a genre, normally I would just do this with a string function and restrict it to certain names with if statements.

However, I’m not sure how to accomplish the same process with an enumerated type, nor do I know if it’s even supposed to be used for that sort of thing. Here is the code if you’re interested.

#include "std_lib_facilities.h"

//Classes-----------------------------------------------------------------------

class Book{
public:
       Book(){}; // default constructor
       //operators
       friend ostream& operator<<(ostream& out, const Book& val);
       bool Book::operator==(const Book& check)
       //enumerators
       enum Genre{
            fiction, nonfiction, periodical, biography, children};
       //member functions
       string title();
       string author();
       int copyright();
       void ISBN();
       bool checkout();
private:
        string title_;
        string author_;
        int copyright_;
        int ISBN1;
        int ISBN2;
        int ISBN3;
        char ISBN4;
        bool checkout_;
};

// Error Function---------------------------------------------------------------

void _error(const string& s)
{
     cout << endl;
     cout << "Error: " << s << endl;
     cout << endl;
}

// Member Functions-------------------------------------------------------------

string Book::title()
{
       cout << "Title: ";
       getline(cin,title_);
       cout << endl;
       return title_;
}

string Book::author()
{
       cout << "Author: ";
       getline(cin,author_);
       cout << endl;
       return author_;
}

int Book::copyright()
{
    cout << "Copyright: ";
    cin >> copyright_;
    cout << endl;
    return copyright_;
}

void Book::ISBN()
{
     cout << "ISBN (Use spaces): ";
     cin >> ISBN1 >> ISBN2 >> ISBN3 >> ISBN4;
     if((ISBN1<0) || (ISBN2<0) || (ISBN3<0) || (ISBN1>9) || (ISBN2>9) || (ISBN3)>9)
               _error("Must be single digit.");
     else if(!isdigit(ISBN4) && !isalpha(ISBN4))
               _error("Must be single digit or letter.");
     else{ cout << endl;
           return;}
}

bool Book::checkout()
{
     char check;
     cout << "Checked out?(Y or N): ";
     cin >> check;
     switch(check){
     case 'Y':
          cout << endl;
          return true;
          break;
     case 'N':
          cout << endl;
          return false;
          break;
     default: 
              _error("Must be Y or N.");}
}

// Operator Overloads-----------------------------------------------------------

ostream& operator<<(ostream& out, const Book& val){
         out << "Title: " << val.title_ << endl;
         out << "Author: " << val.author_ << endl;
         out << "ISBN: " << val.ISBN1 << "-" << val.ISBN2 << "-" << val.ISBN3 << "-" << val.ISBN4 << endl;
         out << endl;
         return out;}

bool Book::operator==(const Book& check){
     return((ISBN1 == check.ISBN1) && (ISBN2 == check.ISBN2) && (ISBN3 == check.ISBN3)
             && (ISBN4 == check.ISBN4));}

// Main-------------------------------------------------------------------------   

int main()
{
    bool finished = false;
    char notfinished;
    while(!finished)
    {
      Book book;
      book.title();
      book.author();
      book.copyright();
      book.ISBN();
      book.checkout();
      cout << "Do you wish to store another book?(Y or N): ";
      cin >> notfinished;
      if(notfinished == 'Y'){ 
                     cin.ignore();
                     cout << endl;}
      else if(notfinished == 'N') finished = true;
      else _error("Must be Y or N");
      }
     keep_window_open();
     }

Note that some things aren’t being used at the moment because the feature they are a part of hasn’t been fully implemented yet (storing in a library, outputting books, etc.)

So what would it take to accept user input for the enumerators listed, if even possible? I was thinking something along the lines of making a Genre variable. Then having a function where the user inputs for cin>>variable. However, I’m guessing that the function wouldn’t understand an input like ‘fiction’ and would only accept the enumerator values and input.

Answer 1

C-style enums are not terribly useful for this purpose, since there’s no way to recover the original string name. You could make some switch-based mechanism, but at that point you may as well just set up your own way of doing it all that works with your user I/O requirements without shoehorning.