What are enumerations and how to use them in C++

In C++ an enumeration (or enum) is a way to define a set of named integer values under the same type.

Each member of an enumeration is a constant that represents a unique integer value (starting at 0 by default and increasing by one for each subsequent member)-

Definition of an Enumeration

To define an enumeration in C++, the keyword enum is used, followed by the name of the enumeration and the members in braces.

enum DaysOfTheWeek
{
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
};

In this example,

• DaysOfTheWeek is an enumeration with seven members: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday.
• By default, Monday has the value 0, Tuesday has the value 1 (and so on)

Enumerations with Specific Values

It is possible to assign specific values to the members of an enumeration (instead of using the default values).

enum DaysOfWeek
{
    Monday = 1,
    Tuesday = 2,
    Wednesday = 3,
    Thursday = 4,
    Friday = 5,
    Saturday = 6,
    Sunday = 7
};

If the numbers are consecutive, you can only number the first of them (the rest will be assigned automatically in sequence).

enum DaysOfWeek
{
    Monday = 1,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
};

Using Enumerations

Assigning Values

Once an enumeration is defined, you can assign values to variables of the enumeration type:

DaysOfTheWeek today = Monday;

Comparing Values

You can also compare these values using equality operators:

if (today == Monday)
{
    std::cout << "Today is Monday." << std::endl;
}

Conversion of Enumerations

Enumerations in C++ are based on integer data types. Therefore, it is possible to convert between an enumeration and its underlying type (which is int by default).

Enum to Integer

You can convert an enumeration value to its integer representation as follows:

int numericValue = static_cast<int>(Wednesday);
std::cout << numericValue << std::endl; // Output: 2

Integer to Enum

You can also convert an integer to an enumeration, as long as the value is valid for the enumeration:

DaysOfTheWeek day = static_cast<DaysOfTheWeek>(4);
std::cout << day << std::endl; // Output: 4 (depending on the implementation, it may require an additional cast to print the name)

Practical Examples

Usage in a Task Management Application

Suppose we are developing an application to manage tasks and we want to use enumerations to represent the status of a task:

enum TaskStatus
{
    Pending,
    InProgress,
    Completed,
    Canceled
};

class Task
{
public:
    std::string Name;
    TaskStatus Status;

    void showStatus()
    {
        std::cout << "The task '" << Name << "' is in status: " << Status << std::endl;
    }
};

int main()
{
    Task task;
    task.Name = "Study for the exam";
    task.Status = InProgress;

    task.showStatus(); // Output: The task 'Study for the exam' is in status: 1
    return 0;
}

Usage in a Game

In game development, enumerations can be useful for representing different types of enemies or game states:

enum EnemyType
{
    Goblin,
    Orc,
    Dragon
};

class Enemy
{
public:
    EnemyType Type;

    void showType()
    {
        std::cout << "This enemy is a: " << Type << std::endl;
    }
};

int main()
{
    Enemy enemy;
    enemy.Type = Dragon;

    enemy.showType(); // Output: This enemy is a: 2
    return 0;
}