## Class type_info_wrapper

boost::log::type_info_wrapper — A simple `std::type_info` wrapper that implements value semantic for type information objects.

## Synopsis

    // In header: <boost/log/utility/type_info_wrapper.hpp>

    class type_info_wrapper {
    public:
      // construct/copy/destruct
      type_info_wrapper();
      type_info_wrapper(type_info_wrapper const &);
      type_info_wrapper(std::type_info const &);

      // public member functions
      explicit operator bool() const;
      std::type_info const & get() const;
      void swap(type_info_wrapper &);
      std::string pretty_name() const;
      bool operator!() const;
      bool operator==(type_info_wrapper const &) const;
      bool operator<(type_info_wrapper const &) const;
    };

## Description

The type info wrapper is very useful for storing type information objects in containers, as a key or value. It also provides a number of useful features, such as default construction and assignment support, an empty state and extended support for human-friendly type names.

### `type_info_wrapper` public construct/copy/destruct

1.     type_info_wrapper();

   Default constructor

   Postconditions: | `!*this == true`

2.     type_info_wrapper(type_info_wrapper const & that);

   Copy constructor

   Parameters: |
   `that` | Source type info wrapper to copy from
   Postconditions: | `*this == that`

3.     type_info_wrapper(std::type_info const & that);

   Conversion constructor

   Parameters: |
   `that` | Type info object to be wrapped
   Postconditions: | `*this == that && !!*this`

### `type_info_wrapper` public member functions

1.     explicit operator bool() const;

   Returns: | `true` if the type info wrapper was initialized with a particular type, `false` if the wrapper was default-constructed and not yet initialized

2.     std::type_info const & get() const;

   Stored type info getter

   Requires: | `!!*this`
   Returns: | Constant reference to the wrapped type info object

3.     void swap(type_info_wrapper & that);

   Swaps two instances of the wrapper

4.     std::string pretty_name() const;

   The method returns the contained type name string in a possibly more readable format than `get().name()`

   Requires: | `!!*this`
   Returns: | Type name string

5.     bool operator!() const;

   Returns: | `false` if the type info wrapper was initialized with a particular type, `true` if the wrapper was default-constructed and not yet initialized

6.     bool operator==(type_info_wrapper const & that) const;

   Equality comparison

   Parameters: |
   `that` | Comparand
   Returns: | If either this object or comparand is in empty state and the other is not, the result is `false`. If both arguments are empty, the result is `true`. If both arguments are not empty, the result is `true` if this object wraps the same type as the comparand and `false` otherwise.

7.     bool operator<(type_info_wrapper const & that) const;

   Ordering operator

   | Note
   The results of this operator are only consistent within a single run of application. The result may change for the same types after rebuilding or even restarting the application.

   Parameters: |
   `that` | Comparand
   Requires: | `!!*this && !!that`
   Returns: | `true` if this object wraps type info object that is ordered before the type info object in the comparand, `false` otherwise