typedObject.h

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/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file typedObject.h
 * @author drose
 * @date 2001-05-11
 */

#ifndef TYPEDOBJECT_H
#define TYPEDOBJECT_H

#include "dtoolbase.h"

#include "typeHandle.h"
#include "register_type.h"
#include "memoryBase.h"

#include <set>

/**
 * This is an abstract class that all classes which use TypeHandle, and also
 * provide virtual functions to support polymorphism, should inherit from.
 * Each derived class should define get_type(), which should return the
 * specific type of the derived class.  Inheriting from this automatically
 * provides support for is_of_type() and is_exact_type().
 *
 * All classes that inherit directly or indirectly from TypedObject should
 * redefine get_type() and force_init_type(), as shown below.  Some classes
 * that do not inherit from TypedObject may still declare TypeHandles for
 * themselves by defining methods called get_class_type() and init_type().
 * Classes such as these may serve as base classes, but the dynamic type
 * identification system will be limited.  Classes that do not inherit from
 * TypedObject need not define the virtual functions get_type() and
 * force_init_type() (or any other virtual functions).
 *
 * There is a specific layout for defining the overrides from this class.
 * Keeping the definitions formatted just like these examples will allow
 * someone in the future to use a sed (or similar) script to make global
 * changes, if necessary.  Avoid rearranging the braces or the order of the
 * functions unless you're ready to change them in every file all at once.
 *
 * What follows are some examples that can be used in new classes that you
 * create.
 *
 * @par In the class definition (.h file):
 * @code
 * public:
 *   static TypeHandle get_class_type() {
 *     return _type_handle;
 *   }
 *   static void init_type() {
 *     <<<BaseClassOne>>>::init_type();
 *     <<<BaseClassTwo>>>::init_type();
 *     <<<BaseClassN>>>::init_type();
 *     register_type(_type_handle, "<<<ThisClassStringName>>>",
 *                   <<<BaseClassOne>>>::get_class_type(),
 *                   <<<BaseClassTwo>>>::get_class_type(),
 *                   <<<BaseClassN>>>::get_class_type());
 *   }
 *   virtual TypeHandle get_type() const {
 *     return get_class_type();
 *   }
 *   virtual TypeHandle force_init_type() {init_type(); return get_class_type();}
 *
 * private:
 *   static TypeHandle _type_handle;
 * @endcode
 *
 * @par In the class .cxx file:
 * @code
 * TypeHandle <<<ThisClassStringName>>>::_type_handle;
 * @endcode
 *
 * @par In the class config_<<<PackageName>>>.cxx file:
 * @code
 * ConfigureFn(config_<<<PackageName>>>) {
 *   <<<ClassOne>>>::init_type();
 *   <<<ClassTwo>>>::init_type();
 *   <<<ClassN>>>::init_type();
 * }
 * @endcode
 */
class EXPCL_DTOOL_DTOOLBASE TypedObject : public MemoryBase {
public:
  INLINE TypedObject() = default;
  INLINE TypedObject(const TypedObject &copy) = default;
  INLINE TypedObject &operator = (const TypedObject &copy) = default;

PUBLISHED:
  // A virtual destructor is just a good idea.
  virtual ~TypedObject();

  // Derived classes should override this function to return get_class_type().
  virtual TypeHandle get_type() const=0;

  // Returns the TypeHandle representing this object's type.
  MAKE_PROPERTY(type, get_type);

  INLINE int get_type_index() const;
  INLINE bool is_of_type(TypeHandle handle) const;
  INLINE bool is_exact_type(TypeHandle handle) const;

public:
  INLINE int get_best_parent_from_Set(const std::set<int> &) const;

  // Derived classes should override this function to call init_type().  It
  // will only be called in error situations when the type was for some reason
  // not properly initialized.
  virtual TypeHandle force_init_type()=0;

  // This pair of methods exists mainly for the convenience of unambiguous
  // upcasting.  Interrogate generates code to call this method instead of
  // making an explicit cast to (TypedObject *); this allows classes who
  // multiply inherit from TypedObject to override these methods and
  // disambiguate the cast.  It doesn't have to be a virtual method, since
  // this is just a static upcast.
  INLINE TypedObject *as_typed_object();
  INLINE const TypedObject *as_typed_object() const;

public:
  static TypeHandle get_class_type() {
    return _type_handle;
  }
  static void init_type();

private:
  static TypeHandle _type_handle;
};

#include "typedObject.I"

#endif