enum class (C++11)

In a Nutshell

A scoped enumeration type that fixes the two classic problems of plain enum: enumerator names polluting the global namespace, and implicit conversion to integers.

Header

No header required (language keyword)

Core API Cheat Sheet

Operation	Signature	Description
Declaration	enum class Name { A, B, C };	Basic scoped enum; the underlying type defaults to int
Specify the underlying type	enum class Name : uint8_t { A, B };	Pins down the underlying type, saving memory
Access an enumerator	Name::A	Must be accessed through the scope operator
Convert to an integer	static_cast<int>(Name::A)	Explicit cast required; no implicit conversion
Opaque declaration	enum class Name : uint8_t;	Forward declaration; the underlying type must be specified
using enum	using enum Name;	(C++20) Brings the enumerators into the current scope

Minimal Example

// Standard: C++11
#include <cstdint>
#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) gives you exact control over memory footprint, a good fit for protocol parsing and register mapping
• Zero runtime overhead; everything is fully resolved at compile time
• Eliminates naming conflicts, which suits modular development in large embedded projects
• Requiring an explicit cast rules out 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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