VariantImpl< Types > Class Template Reference

Type-safe tagged union that can hold any of the types listed in PROMEKI_VARIANT_TYPES. More...

#include <variant.h>

Public Types
enum	Type {   TypeInvalid , TypeBool , TypeU8 , TypeS8 ,   TypeU16 , TypeS16 , TypeU32 , TypeS32 ,   TypeU64 , TypeS64 , TypeFloat , TypeDouble ,   TypeString , TypeDateTime , TypeTimeStamp , TypeSize2D ,   TypeUUID , TypeTimecode , TypeRational }
	Enumerates every type the variant can hold. More...

Public Member Functions
	VariantImpl ()=default
	Default-constructs an invalid (empty) variant holding std::monostate.
template<typename T >
	VariantImpl (const T &value)
	Constructs a variant holding a copy of value.
bool	isValid () const
	Returns true if the variant holds a value other than std::monostate.
template<typename T >
void	set (const T &value)
	Replaces the currently held value with value.
template<typename To >
To	get (Error *err=nullptr) const
	Converts the stored value to the requested type To.
Type	type () const
	Returns the Type enumerator for the currently held value.
const char *	typeName () const
	Returns the human-readable type name of the currently held value.
VariantImpl	toStandardType () const
	Converts complex types to their String representation, leaving simple types unchanged.

Static Public Member Functions
static const char *	typeName (Type id)
	Returns the human-readable C++ type name for the given Type enumerator.
static VariantImpl	fromJson (const nlohmann::json &val)
	Constructs a VariantImpl from a JSON value, inferring the best native type.

Detailed Description

template<typename... Types>
class VariantImpl< Types >

Type-safe tagged union that can hold any of the types listed in PROMEKI_VARIANT_TYPES.

VariantImpl is a thin wrapper around std::variant that adds a Type enum, human-readable type names, and automatic type-conversion logic via the templated get() method. It is not intended to be used directly; instead use

Example

Variant v = 42;
String s = v.get<String>();  // "42"
v.set(String("hello"));
bool valid = v.isValid();    // true
Variant::Type t = v.type();  // Variant::TypeString

the Variant type alias which is instantiated with the concrete type list.

Template Parameters

Types

The set of types the variant can hold (generated from PROMEKI_VARIANT_TYPES).

Member Enumeration Documentation

Type

template<typename... Types>

enum VariantImpl::Type

Enumerates every type the variant can hold.

The enumerator order matches the template argument order so that std::variant::index() can be cast directly to a Type value.

Constructor & Destructor Documentation

VariantImpl()

template<typename... Types>

template<typename T >

VariantImpl< Types >::VariantImpl ( const T &  value )

inline

Constructs a variant holding a copy of value.

Template Parameters

T	The type of the value; must be one of the supported variant types.

Parameters

value

The value to store.

Member Function Documentation

fromJson()

template<typename... Types>

static VariantImpl VariantImpl< Types >::fromJson ( const nlohmann::json &  val )

inlinestatic

Constructs a VariantImpl from a JSON value, inferring the best native type.

Mapping rules:

• null -> invalid (default-constructed) variant
• boolean -> bool
• unsigned integer -> uint64_t
• signed integer -> int64_t
• floating-point -> double
• string -> String
• anything else -> String (via json::dump())

Parameters

val	The JSON value to convert.

Returns

A VariantImpl holding the converted value.

get()

template<typename... Types>

template<typename To >

To VariantImpl< Types >::get ( Error *  err = nullptr ) const

inline

Converts the stored value to the requested type To.

The method uses std::visit with a compile-time conversion matrix. If the stored type is already To, the value is returned directly. Otherwise an appropriate conversion is attempted (numeric casts, string parsing, toString() calls, etc.). When no conversion path exists, a default-constructed To is returned and err (if non-null) is set to Error::Invalid.

Template Parameters

To	The desired result type.

Parameters

err	Optional pointer to an Error that receives Error::Ok on success or Error::Invalid when the conversion is not possible.

Returns

The converted value, or a default-constructed To on failure.

set()

template<typename... Types>

template<typename T >

void VariantImpl< Types >::set ( const T &  value )

inline

Replaces the currently held value with value.

Template Parameters

T	The type of the new value; must be one of the supported variant types.

Parameters

value

The value to store.

toStandardType()

template<typename... Types>

VariantImpl VariantImpl< Types >::toStandardType ( ) const

inline

Converts complex types to their String representation, leaving simple types unchanged.

Types such as String, DateTime, TimeStamp, Size2Du32, UUID, Timecode, and Rational are converted to String via get<std::string>(). All other types (numeric, bool, invalid) are returned as-is.

Returns

A new VariantImpl containing either the original value or its String representation.

typeName()

template<typename... Types>

static const char * VariantImpl< Types >::typeName ( Type  id )

inlinestatic

Returns the human-readable C++ type name for the given Type enumerator.

Parameters

[in]

id

The Type enumerator value.

Returns

A null-terminated string such as "bool", "String", etc.

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The documentation for this class was generated from the following file:

• include/promeki/core/variant.h