access-casted-o.hpp File Reference

Helper for accessing a value, employing either conversion or downcast, depending on the relation of the source type (type of the original value) and the target type (type we need within the usage context). More...

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Description

Helper for accessing a value, employing either conversion or downcast, depending on the relation of the source type (type of the original value) and the target type (type we need within the usage context).

When instantiating AcessCasted<TAR>, we get a template static function AcessCasted<TAR>::access<SRC>(SRC& elm), but the actual implementation is chosen using std::type_traits. If no sensible implementation can be selected, EmptyVal<TAR>::create() is invoked instead, which by default creates a NULL value or similar by using the no-argument ctor of the type TAR. Alternatively, you may define an specialisation of EmptyVal, e.g. throwing an exception instead of creating a NULL value.

Deprecated:

old obsolete version ///////////////////////////////////////////TICKET #738 clean-up access-casted, rewrite variant (4/2015)

Todo:

This is the obsoleted old version: It was excessively permissive, which I've learned to view as a danger, since it encourages a sloppy programming style.

See also

lumiera::WrapperPtr usage example to access a variant record

lib::InPlaceAnyHolder usage example to access a subclass in embedded storage

Definition in file access-casted-o.hpp.

#include <type_traits>

Namespaces
namespace	util
namespace	util::anonymous_namespace{access-casted-o.hpp}

Classes
struct	can_cast< SRC, TAR >
struct	can_cast< SRC *, TAR * >
struct	can_cast< SRC *&, TAR * >
struct	can_cast< SRC &, TAR & >
struct	hasRTTI< T >
struct	use_dynamic_downcast< SRC, TAR >
struct	use_static_downcast< SRC, TAR >
struct	use_conversion< SRC, TAR >
struct	EmptyVal< X >
struct	EmptyVal< X *& >
struct	NullAccessor< RET >
struct	AccessCasted_O< TAR >