enum class (C++11)

In a Nutshell

A scoped enumeration type that resolves the issues of traditional enum polluting the global namespace and implicitly converting to integers.

Header

None required (language keyword)

Core API Quick Reference

Operation	Signature	Description
Declaration	enum class Name { A, B, C };	Basic scoped enumeration, default underlying type is int
Specify underlying type	enum class Name : uint8_t { A, B };	Fixed underlying type, saves memory
Access enumerator	Name::A	Must be accessed via the scope operator
Convert to integer	static_cast<int>(Name::A)	Requires explicit cast, no implicit conversion
Opaque declaration	enum class Name : uint8_t;	Forward declaration, requires specifying the underlying type
using enum	using enum Name;	(C++20) Introduces enumerators into the current scope

Minimal Example

// Standard: C++11
#include <iostream>

int main() {
    enum class Color : uint8_t { red, green = 20, blue };
    Color r = Color::blue;

    switch (r) {
        case Color::red:   std::cout << "red\n";   break;
        case Color::green: std::cout << "green\n"; break;
        case Color::blue:  std::cout << "blue\n";  break;
    }

    // int n = r; // error
    int n = static_cast<int>(r);
    std::cout << n << '\n'; // 21
}

Embedded Applicability: High

• Specifying the underlying type (e.g., uint8_t, uint32_t) allows precise control over memory footprint, ideal for protocol parsing and register mapping
• Zero runtime overhead, fully resolved at compile time
• Eliminates naming conflicts, suitable for modular development in large embedded projects
• Explicit type conversions prevent accidental integer comparisons, improving code safety

Compiler Support

GCC	Clang	MSVC
4.7	3.1	2010

See Also

• cppreference: Enumeration declaration

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