Compile-time metadata about an enum type.

The primary template is undefined. Specializations are generated automatically for enums registered with PW_ENUM.

Specializations provide the following members. Enumerators that share a value (aliases) are treated as a single distinct value.

• enum_type — the enum type itself.
• underlying_type — std::underlying_type_t<enum_type>.
• kName — unqualified enum name, e.g. "MyEnum".
• kFullyQualifiedName — fully qualified enum name, e.g. "::my::ns::MyEnum".
• kTokenDomain — the pw_tokenizer domain the enum is tokenized in.
• kDistinctValueCount — number of distinct values; equals kValues.size().
• kIsContiguous — whether the distinct values cover every integer from kMin to kMax with no gaps.
• kMin / kMax — smallest and largest enumerator values.
• kValues — std::array<enum_type, kDistinctValueCount> of the distinct values in ascending order.
• IsValid(value) — returns whether an enumerator or integer value is a valid enumerator; see pw::IsValidEnum.

Example

// A fixed-size array indexed by any contiguous PW_ENUM enum. Aliased

// enumerators share an entry, and enums that do not start at 0 are offset by

// kMin.

template <typename Enum, typename T>

class EnumArray {

public:

using Traits = pw::EnumTraits<Enum>;

static_assert(Traits::kIsContiguous, "EnumArray requires a contiguous enum");

constexpr T& operator[](Enum value) { return values_[Index(value)]; }

constexpr const T& operator[](Enum value) const {

return values_[Index(value)];

}

constexpr size_t size() const { return Traits::kDistinctValueCount; }

private:

static constexpr size_t Index(Enum value) {

return static_cast<size_t>(

static_cast<typename Traits::underlying_type>(value) -

static_cast<typename Traits::underlying_type>(Traits::kMin));

}

std::array<T, Traits::kDistinctValueCount> values_{};

};

pw::EnumTraits

Definition: traits.h:60

Source: pw_enum/examples/traits.cc

Warning

Do not specialize pw::EnumTraits by hand. Specializations are identified by an internal tag that only the code generator emits, so a hand-written one is not recognized by pw::has_enum_traits_v and is rejected by pw::IsValidEnum. To get traits for an enum, register it with PW_ENUM.