Class template type_index_facade

boost::typeindex::type_index_facade

Synopsis

// In header: <boost/type_index/type_index_facade.hpp>

template<typename Derived, typename TypeInfo> 
class type_index_facade {
public:
  // types
  typedef TypeInfo type_info_t;

  // public member functions
  const char * name() const noexcept;
  std::string pretty_name() const;
  bool equal(const Derived &) const noexcept;
  bool before(const Derived &) const noexcept;
  std::size_t hash_code() const noexcept;

  // protected member functions
  const char * raw_name() const noexcept;
  const type_info_t & type_info() const noexcept;

  // protected static functions
  template<typename T> static Derived type_id() noexcept;
  template<typename T> static Derived type_id_with_cvr() noexcept;
  template<typename T> static Derived type_id_runtime(const T &) noexcept;
};

Description

This class takes care about the comparison operators, hash functions and ostream operators. Use this class as a public base class for defining new type_info-conforming classes.

Example:

class stl_type_index: public type_index_facade<stl_type_index, std::type_info> 
{
public:
    typedef std::type_info type_info_t;
private:
    const type_info_t* data_;

public:
    stl_type_index(const type_info_t& data) noexcept
        : data_(&data)
    {}
// ...
};

	Note
	Take a look at the protected methods. They are not defined in type_index_facade. Protected member functions raw_name() must be defined in Derived class. All the other methods are mandatory.

See Also:

'Making a custom type_index' section for more information about creating your own type_index using type_index_facade.

Template Parameters

```
typename Derived
```
Class derived from type_index_facade.
```
typename TypeInfo
```
Class that will be used as a base type_info class.

`type_index_facade` public member functions

```
const char * name() const noexcept;
```
Override: This function may be redefined in Derived class. Overrides must not throw.

Returns:

Name of a type. By default returns Derived::raw_name().
```
std::string pretty_name() const;
```
Override: This function may be redefined in Derived class. Overrides may throw.

Returns:

Human readable type name. By default returns Derived::name().
```
bool equal(const Derived & rhs) const noexcept;
```
Override: This function may be redefined in Derived class. Overrides must not throw.

Returns:

True if two types are equal. By default compares types by raw_name().
```
bool before(const Derived & rhs) const noexcept;
```
Override: This function may be redefined in Derived class. Overrides must not throw.

Returns:

True if rhs is greater than this. By default compares types by raw_name().
```
std::size_t hash_code() const noexcept;
```
Override: This function may be redefined in Derived class. Overrides must not throw.

Note

Derived class header must include <boost/functional/hash.hpp>, unless this function is redefined in Derived class to not use boost::hash_range().

Returns:

Hash code of a type. By default hashes types by raw_name().

`type_index_facade` protected member functions

```
const char * raw_name() const noexcept;
```
Override: This function must be redefined in Derived class. Overrides must not throw.

Returns:

Pointer to unredable/raw type name.
```
const type_info_t & type_info() const noexcept;
```
Override: This function may be redefined in Derived class. Overrides must not throw.

Returns:

Const reference to underlying low level type_info_t.

`type_index_facade` protected static functions

```
template<typename T> static Derived type_id() noexcept;
```
This is a factory method that is used to create instances of Derived classes. boost::typeindex::type_id() will call this method, if Derived has same type as boost::typeindex::type_index.

Override: This function may be redefined and made public in Derived class. Overrides must not throw. Overrides must remove const, volatile && and & modifiers from T.

Template Parameters:

T

Type for which type_index must be created.

Returns:

type_index for type T.
```
template<typename T> static Derived type_id_with_cvr() noexcept;
```
This is a factory method that is used to create instances of Derived classes. boost::typeindex::type_id_with_cvr() will call this method, if Derived has same type as boost::typeindex::type_index.

Override: This function may be redefined and made public in Derived class. Overrides must not throw. Overrides must not remove const, volatile && and & modifiers from T.

Template Parameters:

T

Type for which type_index must be created.

Returns:

type_index for type T.
```
template<typename T> 
  static Derived type_id_runtime(const T & variable) noexcept;
```
This is a factory method that is used to create instances of Derived classes. boost::typeindex::type_id_runtime(const T&) will call this method, if Derived has same type as boost::typeindex::type_index.

Override: This function may be redefined and made public in Derived class.

Parameters:

variable

Variable which runtime type will be stored in type_index.

Returns:

type_index with runtime type of variable.

	Note
	Derived class header must include <boost/functional/hash.hpp>, unless this function is redefined in Derived class to not use boost::hash_range().

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