BloombergLP::bdlb::Variant

Discriminated union that holds a value of one of up to 20 alternative types.

Synopsis

Declared in <bdlb_variant.h>

template<class... TYPES>
class Variant
    : public VariantImp<bslmf::TypeList<TYPES...>::ListType>

Description

This class provides a "variant" type, i.e., a type capable of storing values from a list of template parameter types. Note that if the number N of types is smaller than 20, unused parameters default to bslmf::Nil, but it is more economical to use VariantN, which accepts exactly N template arguments, as this leads to shorter symbols and debug string information.

Base Classes

Name

Description

VariantImp<bslmf::TypeList<TYPES...>::ListType>

This class provides the implementation of Variant (except for the creators) given a list of template parameter TYPES.

Member Functions

Name

Description

Variant [constructor]

Constructors

Assignment operators

apply overloads

applyRaw overloads

Assign the specified TYPE value to this object.

Assign value converted to TYPE to this object.

DEPRECATED: Do not use.

bdexStreamOut

DEPRECATED: Do not use.

createInPlace

Emplace a TYPE instance constructed from arguments.

Return whether this variant currently holds a TYPE value.

Return whether this variant currently holds no value.

maxSupportedBdexVersion

DEPRECATED: Do not use.

Format this object to the specified output stream.

Destroy the current value held by this variant (if any), and reset this variant to the unset state.

Swap the value of this object with other.

the overloads

Return the 1‐based index of the held type, or 0 if unset.

Return typeid(void).

operator BloombergLP::bslmf::NestedTraitDeclaration<Variant, HasPrintMethod>

Nested trait declaration for bdlb::HasPrintMethod.

operator BloombergLP::bslmf::NestedTraitDeclaration<Variant, IsBitwiseCopyable, Traits::k_VARIANT_IS_BITWISE_COPYABLE>

Nested trait declaration for bslmf::IsBitwiseCopyable.

operator BloombergLP::bslmf::NestedTraitDeclaration<Variant, IsBitwiseMoveable, Traits::k_VARIANT_IS_BITWISE_MOVEABLE>

Nested trait declaration for bslmf::IsBitwiseMoveable.

operator BloombergLP::bslmf::NestedTraitDeclaration<Variant, UsesBslmaAllocator, Traits::k_VARIANT_USES_BSLMA_ALLOCATOR>

Nested trait declaration for bslma::UsesBslmaAllocator.

operator BloombergLP::bslmf::NestedTraitDeclaration<VariantImp, HasPrintMethod>

Nested trait declaration for bdlb::HasPrintMethod.

operator BloombergLP::bslmf::NestedTraitDeclaration<VariantImp, IsBitwiseCopyable, Traits::k_VARIANT_IS_BITWISE_COPYABLE>

Nested trait declaration for bslmf::IsBitwiseCopyable.

operator BloombergLP::bslmf::NestedTraitDeclaration<VariantImp, IsBitwiseMoveable, Traits::k_VARIANT_IS_BITWISE_MOVEABLE>

Nested trait declaration for bslmf::IsBitwiseMoveable.

operator BloombergLP::bslmf::NestedTraitDeclaration<VariantImp, UsesBslmaAllocator, Traits::k_VARIANT_USES_BSLMA_ALLOCATOR>

Nested trait declaration for bslma::UsesBslmaAllocator.

Non-Member Functions

Name

Description

Return whether lhs and rhs do not have the same value.

Grant the equality comparison operator access to this class's private members.

Return whether lhs and rhs have the same value.

Swap the values of the specified a and b objects.

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