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KwargsValue class

A value wrapper capable of storing values of any type, similar to std::any.

Syntax

class KwargsValue;

Members

Constructors

Name Description
KwargsValue() Default constructor.
KwargsValue(const KwargsValue&) Copy constructor.
KwargsValue(KwargsValue&&) Move constructor.
KwargsValue(const _Tp&) Stores a value or a pointer to a value of type _Tp.
KwargsValue(_Tp&&) Stores a value of type _Tp with move semantics.
KwargsValue(const char (&)[_Size]) Partial specialization for string literals, stores the pointer to the first character.

Destructor

Name Description
~KwargsValue Destructor.

Functions

Name Description
typeName Returns the string name of the last _Tp used in construction. Compiler-dependent.
typeHashCode Returns the hash code of the last _Tp using std::type_info::hash_code().
valueTypeHashCode Returns the hash code of _Tp::value_type if available; otherwise same as typeHashCode().
hasValueType Checks whether _Tp::value_type exists.
isSameType Checks whether the stored type _Tp matches a given type.
isInteger Checks if _Tp is an integer or enum type.
isRealNumber Checks if _Tp is a floating-point type.
isEnum Checks if _Tp is an enumeration.
isStdArray Checks if _Tp is std::array.
isIterable Checks if _Tp is an iterable container.
pointer Returns a pointer to the internal value. Ensure the type layout matches before dereferencing.
reference Dereferences pointer().
value Retrieves the stored value with optional implicit conversion.
size Returns sizeof(_Tp) at construction time.

Operators

Name Description
operator= Assignment operator.

KwargsValue

Default constructor

Initializes with a default int value of 0.

constexpr KwargsValue() = default;

Copy/Move/Template constructor

Constructs from any value. If the type is a struct, union, or larger than 8 bytes, a pointer to the object is stored (lifetime considerations apply). Otherwise, the value is stored via byte-level copy.

template<typename _Tp>
constexpr KwargsValue(const _Tp& __value) noexcept;

For rvalue references, constructs by dynamically allocating the object and moving it.

template<typename _Tp>
constexpr KwargsValue(_Tp&& __value);

Partial specialization for string literals; stores a pointer to the first character.

template<std::size_t _Size>
constexpr KwargsValue(const char (&__value)[_Size]) noexcept;

~KwargsValue

If the value was dynamically allocated during construction, it is destroyed and freed.

_KWARGS_DESTRUCTOR_CONSTEXPR ~KwargsValue() noexcept;

Tip

_KWARGS_DESTRUCTOR_CONSTEXPR is defined as constexpr in C++20 and inline in C++17.

typeName

Returns the string representation of _Tp. The result may vary by compiler.

constexpr std::string_view typeName() const noexcept;

typeHashCode

Returns the hash code of _Tp.

constexpr std::size_t typeHashCode() const noexcept;

valueTypeHashCode

Returns the hash code of _Tp::value_type, or falls back to typeHashCode() if unavailable.

constexpr std::size_t valueTypeHashCode() const noexcept;

hasValueType

Checks for the existence of _Tp::value_type.

constexpr bool hasValueType() const noexcept;

isSameType

Checks whether the stored type _Tp matches the provided type.

template<typename _Tp>
constexpr bool isSameType() const noexcept;

Tip

For enums, it compares the underlying type instead.

isInteger

Checks if _Tp is an integer or enum.

constexpr bool isInteger() const noexcept;

isRealNumber

Checks if _Tp is a floating-point type.

constexpr bool isRealNumber() const noexcept;

isEnum

Checks if _Tp is an enum.

constexpr bool isEnum() const noexcept;

isStdArray

Checks if _Tp is a std::array.

constexpr bool isStdArray() const noexcept;

isIterable

Checks if _Tp is an iterable container type.

constexpr bool isIterable() const noexcept;

Tip

Iterable containers are those with .begin() and .end() member functions.

pointer

Returns a pointer to the stored value. Ensure type layout compatibility before dereferencing.

template<typename _Tp>
constexpr _Tp* pointer() noexcept;

template<typename _Tp>
constexpr const _Tp* pointer() const noexcept;

reference

Dereferences the pointer returned by pointer().

template<typename _Tp>
constexpr _Tp& reference() noexcept
{ return *pointer<_Tp>(); }

template<typename _Tp>
constexpr const _Tp& reference() const noexcept
{ return *pointer<_Tp>(); }

value

Returns the stored value of type _Tp, with optional conversion if types differ.

template<typename _Tp>
constexpr std::enable_if_t<..., _Tp> value() const noexcept;

Note

Due to type erasure, direct copying is not supported.

Warning

If conversion fails, assert() is triggered. If NODEBUG is defined, it returns a default-constructed _Tp.

Why not use throw for errors?

In constexpr functions, which may execute at compile-time, throw is not permitted since it's a runtime operation.

size

Returns the size of the stored type _Tp. If _Tp is a string literal, returns the number of characters.

constexpr std::uint32_t size() const noexcept;

operator=

Performs copy or move assignment and updates the stored type to that of the __other's _Tp.

constexpr KwargsValue& operator=(const KwargsValue& __other);

constexpr KwargsValue& operator=(KwargsValue&& __other) noexcept;