Enum

An enum is another type you can create. This gives you the ability to define a list of values that the type accepts.

Annotated genre_data enum and example variables

An enum:

• Is a building block that you can create and use in your code.
• Is a declaration of a new type - you can use this to create variables, parameters, and return these values from functions.
• Lists the values that the type accepts.
• Is actually stored as an integer - starting at 0 for the first value.
• Can use a type cast to convert to and from an integer value.

When you use an enum, you can:

• Use one of the names you declare in the type.
• Convert it to an integer or from an integer when needed.
• Use a switch statement with branches for the different values.

Example

In this program we create a new genre_data type. This means we can create and work with values that represent genres within our program.

#include "splashkit.h"

// Access read_integer and read_string in utilities
#include "utilities.h"

using std::to_string;

/**
 * Genre data captures the list of genre's captured in the software.
 */
enum genre_data
{
    FANTASY = 0,
    SCIENCE_FICTION,
    MYSTERY,
    ROMANCE,
    COOKING,
    NONFICTION
};

// Get the number of genres. Cast the last
// one to an integer and add one as it start from 0
const int GENRE_COUNT = (int)NONFICTION + 1;

/**
 * Convert a genre to a string
 *
 * @param genre the data to convert
 */
string to_string(genre_data genre)
{
  switch(genre)
  {
    case FANTASY:
      return "fantasy";
    case SCIENCE_FICTION:
      return "science fiction";
    case MYSTERY:
      return "mystery";
    case ROMANCE:
      return "romance";
    case COOKING:
      return "cooking";
    case NONFICTION:
      return "nonfiction";
    default:
      // While we expect the above, it can be broken
      // when we cast from an integer...
      return "unknown";
  }
}

/**
 * Read in a genre value from the user.
 *
 * @param prompt a message to prompt the user with
 * @return a genre
 */
genre_data read_genre(string prompt)
{
  // Create a book variable, and initialise it
  genre_data result;
  int raw;

  // Loop through the integers that relate to the genre
  // Output as the list of options to choose from
  // Starting at 1
  for(raw = 0; raw < GENRE_COUNT; raw++)
  {
    // convert the raw integer value to a genre_data
    // and then conver that to a string
    write_line(to_string(raw + 1) + ": " + to_string((genre_data)raw));
  }

  // Read in the integer value of the genre
  // - user enters 1 to GENRE_COUNT. So -1 needed.
  // - provide a range if you can
  raw = read_integer(prompt) - 1;

  // Convert the raw integer data to a genre
  return (genre_data) raw;
}

int main()
{
  // Create a test_genre
  genre_data test_genre;

  // Assign a value
  test_genre = MYSTERY;

  // Output its name and integer value
  write_line(to_string(test_genre) + " has value " + to_string((int)test_genre));

  // Assign an invalid value - by casting an integer
  test_genre = (genre_data)157;

  // Output its name and integer value
  write_line(to_string(test_genre) + " has value " + to_string((int)test_genre));

  // Read in genre data from the user
  test_genre = read_genre("Enter a genre: ");

  // Output its name and integer value
  write_line(to_string(test_genre) + " has value " + to_string((int)test_genre));

  return 0;
}