4.5 KiB
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| variant (legacy) |
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Header: variant.h
Similar to: std::variant
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Deprecated for C++11 and above.
This version is automatically selected if either the compiler does not support C++11, or ETL_USE_LEGACY_VARIANT is defined.
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A class that can contain one a several specified types in a type safe manner.
Supports up to eight types.
Supplies a nested reader visitor class that allows type safe access via sets of overloaded virtual read functions for each type.
Accepts etl::visit since 20.28.0.
If ETL_USE_LEGACY_VARIANT is defined then etl::variant is in the etl namespace.
If ETL_USE_LEGACY_VARIANT is not defined then etl::variant is in the etl::legacy namespace.
Since: 20.30.0.
Constructors
variant()
Description
Default constructor.
template <typename T>
variant(T value)
Description
Construct from value.
A static assert will occur if T is not a supported type.
Operations
template <typename T>
variant& operator =(typename parameter_type<T>::type value)
Description
Assigns a value.
A static assert occurs if the type T is not supported.
If C++11 is not supported
template <typename T, typename TP1>
T& emplace(const TP1& value1)
template <typename T, typename TP1, typename TP2>
T& emplace(const TP1& value1, const TP2& value2)
template <typename T, typename TP1, typename TP2, typename TP3>
T& emplace(const TP1& value1, const TP2& value2, const TP3& value3)
template <typename T, typename TP1, typename TP2, typename TP3, typename TP4>
T& emplace(const TP1& value1, const TP2& value2, const TP3& value3, const TP4& value4)
Description
Construct a T from multiple arguments.
If C++11 or greater is supported
template <typename T, typename... Args>
T& emplace(Args&&... args)
Description
Construct a Ts in-place using the supplied parameters.
void clear()
Description
Clears the variant of holding any type.
Access
template <typename T>
T& get()
Gets a value.
If T is a type not supported by the variant then a static assert occurs.
If T is a type that is not the type currently stored then a variant_incorrect_type_exception() error is raised.
If asserts or exceptions are not enabled then undefined behaviour occurs.
const template <typename T>
T& get() const
Gets a value.
If T is a type not supported by the variant then a static assert occurs.
If T is a type that is not the type currently stored then a variant_incorrect_type_exception() error is raised.
If asserts or exceptions are not enabled then undefined behaviour occurs.
T* upcast_ptr<T>()
const T* upcast_ptr<T>() const
For variant types that are polymorphic.
Up-casts the variant to type T*.
Types that cannot be up-cast will result in a nullptr return.
Since: 20.30.0
T& upcast<T>()
const T& upcast<T>() const
For variant types that are polymorphic.
Up-casts the variant to type T.
Types that cannot be up-cast will result in a runtime error etl::variant_not_a_base.
Since: 20.30.0
bool is_base_of<T>() const
Tests if the type T is a base of the current variant type.
Since: 20.30.0
call(reader& r)
Calls the appropriate overloaded r.read() function with the value.
template <typename T>
variant& operator =(typename parameter_type<T>::type value)
Assigns a value.
A static assert occurs if the type T is not supported.
Any value stored in the variant can be implicitly cast to its current type.
If the implicit cast is to a type not supported by the variant then a static assert occurs.
If the implicit cast is to a type that is not the type currently stored then a etl::variant_incorrect_type_exception error is raised.
Tests
template <typename T>
static bool is_supported_type()
Returns true if T is supported by the variant, otherwise false.
bool is_same_type(const variant& other) const
Returns true if the variant holds the same type as the other, otherwise false.
bool is_valid() const
Returns true if the variant holds a valid value, otherwise false.
template <typename T>
bool is_type() const
Returns true if T is the type currently stored in the variant, otherwise false.
Visitation
For STL style etl::visit
20.28.0
The ETL implements an STL style visit function.