## vptr_vector

### Synopsis

Defined in <boost/openmethod/policies/vptr_vector.hpp>.

```c++
namespace boost::openmethod::policies {

template<class Policy>
class vptr_vector : Base {
  public:
    template<typename ForwardIterator>
    static auto register_vptrs(ForwardIterator first, ForwardIterator last) -> void;

    template<class Class>
    static auto dynamic_vptr(const Class& arg) -> const vptr_type&;
};

}
```

### Description

`vptr_vector` is an implementation or `external_vptr` that keeps the pointers to
the v-tables in a `std::vector`. If `Policy` contains `indirect_vptr`, a level
of indirection is added, making the policy usable in presence of dynamic
loading.

`Policy` is the policy containing the policy.

### Members

#### register_vptrs

```c++
template<typename ForwardIterator>
auto register_vptrs(ForwardIterator first, ForwardIterator last) -> void;
```

Stores the pointers to v-tables in a vector, indexed by the (possibly hashed)
`type_id`s of the classes registered in `Policy`.

If `Policy` contains a `type_hash` policy, call its `hash_initialize`
function, and uses it to convert the `type_id`{empty}s to an index.

#### dynamic_vptr

```c++
template<class Class>
auto dynamic_vptr(const Class& object) -> const vptr_type&;
```

Returns a pointer to the v-table for `object` (by reference).

Obtains a `type_id` for `object` using `Policy::dynamic_type`. If _Policy_
contains a `type_hash` policy, uses it to convert the result to an index;
otherwise, uses the `type_id` as the index.