PolymorphicValue< IFA, storage, CPY > Class Template Reference

#include "lib/polymorphic-value.hpp"

Description

template<class IFA, size_t storage, class CPY = IFA>
class lib::PolymorphicValue< IFA, storage, CPY >

Template to build polymorphic value objects.

Inline buffer with value semantics, yet holding and owning an object while concealing the concrete type, exposing only the public interface. Access to the contained object is by implicit conversion to this public interface. The actual implementation object might be placed into the buffer through a builder function; later, this buffer may be copied and passed on without knowing the actual contained type.

For using PolymorphicValue, several assumptions need to be fulfilled

• any instance placed into the opaque buffer is below the specified maximum size
• the caller cares for thread safety. No concurrent get calls while in mutation!

Warning

when a create or copy-into operation fails with exception, the whole PolymorphicValue object is in undefined state and must not be used henceforth.

Definition at line 374 of file polymorphic-value.hpp.

Public Types
typedef IFA	Interface

Public Member Functions
	PolymorphicValue (PolymorphicValue const &o)
Interface &	getPayload ()
	operator Interface & ()
	operator Interface const & () const
Interface *	operator-> () const
PolymorphicValue &	operator= (PolymorphicValue const &o)

Static Public Member Functions
template<class IMP , typename... ARGS>
static PolymorphicValue	build (ARGS &&... args)

Classes
class	Adapter
	Implementation Helper: add support for copy operations. More...

Friends
bool	operator!= (PolymorphicValue const &v1, PolymorphicValue const &v2)
bool	operator== (PolymorphicValue const &v1, PolymorphicValue const &v2)

Protected Member Functions
template<class IMP , typename... ARGS>
	PolymorphicValue (IMP *, ARGS &&... args)

Private Types
enum	{ siz = storage + _Traits::ADMIN_OVERHEAD }
typedef _Traits::Assignment	_AssignmentPolicy
typedef _Traits::CopyAPI	_CopyHandlingAdapter
typedef polyvalue::Trait< CPY >	_Traits
template<typename IMP >
using	TypeSelector = Adapter< IMP > *

Private Member Functions
template<class IMP , typename... ARGS>
	PolymorphicValue (TypeSelector< IMP >, ARGS &&... args)
IFA &	accessEmbedded () const
_CopyHandlingAdapter &	accessHandlingInterface () const
void	destroyEmbedded ()

Private Attributes
std::byte	buf_ [siz]
	Storage for embedded objects.

Constructor & Destructor Documentation

PolymorphicValue() [1/2]

PolymorphicValue ( TypeSelector< IMP >  , ARGS &&...  args  )

inlineprivate

this is the actual working ctor, which must care to decorate the desired impl type with an additional adapter to support copy operations.

Definition at line 460 of file polymorphic-value.hpp.

PolymorphicValue() [2/2]

PolymorphicValue ( IMP *  , ARGS &&...  args  )

inlineprotected

ctor for subclasses and builder functions. The constructor requires an additional type-selector argument. On invocation, the desired subclass/implementation object is immediately planted into the embedded buffer, passing through the given ctor arguments.

See also

factory functions for public use

Definition at line 476 of file polymorphic-value.hpp.

Inheritance diagram for PolymorphicValue< IFA, storage, CPY >:

Collaboration diagram for PolymorphicValue< IFA, storage, CPY >:

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

• polymorphic-value.hpp