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openmethod/doc/rtti.adoc
Jean-Louis Leroy 5e0fa8ee4b inception
2025-03-08 15:31:25 -05:00

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## rtti
### Synopsis
Defined in <boost/openmethod/policies/basic_policy.hpp>.
```c++
namespace boost::openmethod::policies {
struct rtti {};
} // boost::openmethod::policies
```
### Description
The `rtti` facet provides type information for classes and objects, implements
downcast in presence of virtual inheritance, and writes descriptions of types to
an `ostream`-like object.
### Requirements
#### static_type
```c++
template<class Class>
static auto static_type() -> type_id;
```
Returns a `type_id` for `Class`.
#### dynamic_type
```c++
template<class Class>
static auto dynamic_type(const Class& obj) -> type_id;
```
Returns a `type_id` for an object's dynamic type.
#### type_name
```c++
template<typename Stream>
static auto type_name(type_id type, Stream& stream) -> void;
```
Writes a description of `type` to `stream`.
This requirement is optional. `rtti` provides a default implementation that writes `typeid({type})` to `stream`.
#### type_index
```c++
static auto type_index(type_id type) -> /* unspecified */;
```
Returns a unique key for `type`. Required only for RTTI systems that assign more
than one type "identifiers" to a type. For example, standard RTTI allows
implementations to have multiple instances of `std::type_info` for the same
type.
#### dynamic_cast_ref
```c++
template<typename D, typename B>
static auto dynamic_cast_ref(B&& obj) -> D;
```
Casts `obj` to `D`. Required only if using virtual inheritance.