When to Use Enum Instead of Macro in C++?

In C++, both enums and macros are used to define symbolic names for a set of values. However, there are certain situations where using an enum is more beneficial than using a macro. In this article, we will learn when to use an enum instead of a macro in C++.

When to Prefer Enum Instead of Macro?

In C++, prefer to use an Enum instead of a Macro in the following cases:

1. Type Safety

Enums are type-safe, which means the compiler checks the assignment of enum variables and ensures that the assigned value is within the valid range. On the other hand, macros are not type-safe, which can lead to bugs that are hard to detect.

Example:

C++

// C++ program to use enum to ensure type safety

#include <iostream>
using namespace std;

// Enum defining different colors
enum Color { Red, Green, Blue };

// Function to print the color based on enum value
void printColor(Color color)
{
    switch (color) {
    case Red:
        cout << "Red";
        break;
    case Green:
        cout << "Green";
        break;
    case Blue:
        cout << "Blue";
        break;
    }
    cout << endl;
}

int main()
{
    // Initialize a variable of type Color with Red
    Color color = Red;
    // Attempting to assign a value outside the enum range
    // would cause a compilation error i.e. color = 5; would
    // cause a compilation error, ensuring type safety.
    // Print the color
    printColor(color);

    return 0;
}

Output

Red

2. Scope Control

Enums have scope control, means we can define them within classes or namespaces, preventing naming conflicts. Macros, however, are always defined in the global scope, which can lead to naming conflicts.

Example:

C++

// C++ program to demonstrate Scope Control and Strongly
// Typed Enums

#include <iostream>
using namespace std;

enum class Fruit { Apple, Banana, Cherry };

int main()
{
    // Scope Control and Strongly Typed Enums
    Fruit fruit = Fruit::Banana; // Scoped enumeration
                                 // prevents name conflicts
    cout << "Fruit: " << static_cast<int>(fruit) << endl;
    return 0;
}

Output

Fruit: 1

3. Automatic Assignment

Enum values are automatically assigned integer values starting from 0, if not explicitly defined that makes it convenient for sequentially ordered values.

Example:

C++

// C++ program to demonstrate  Automatic Assignment in enum

#include <iostream>
using namespace std;

enum assignId { Ram, Mohit, Ria };

int main()
{
    // Automatic Assignment
    assignId id = Mohit; // Automatically assigned a id of 1
    cout << "Id: " << id << endl;
    return 0;
}

Output

Id: 1

4. Debugging

Enums are easier to debug than macros because when we use a macro, the preprocessor replaces it with its value before the code is compiled, making it difficult to debug whereas enum retain their names throughout the compilation process, making them easier to debug.

5. Integration with Tools

Enums are better integrated with tools like IDEs and static analyzers. These tools can provide features like auto-completion, refactoring support, and more for enums, but not for macros.

6. Performance

The performance of enums and macros is generally the same. However, in some cases, using an enum can result in more efficient code because the compiler has more information about the enum’s type and can optimize accordingly.