==================================
``transfer_ownership`` transformer
==================================

.. contents:: Table of contents

----------
Definition
----------

"transfer_ownership" transformer changes type of the function argument, from
``T*`` to ``std::auto_ptr<T>``. This transformer was born to provide the answer
to `How can I wrap a function which needs to take ownership of a raw pointer?`_
FAQ.

.. _`How can I wrap a function which needs to take ownership of a raw pointer?` : http://boost.org/libs/python/doc/v2/faq.html#ownership

"transfer_ownership" transformer takes one argument, name or index of the
original function argument. The argument type should be "pointer".

New in version greater than 0.8.5.

-------
Example
-------

.. code-block:: C++

  struct resource_t{...};

  void do_smth(resource_t* r){
      ...
  }

Lets say that you need to expose "do_smth" function. According to the FAQ, you
have to create small wrapper, which will take ``std::auto_ptr`` as an argument.
The following `Py++`_ code does it for you:

  .. code-block:: Python

     from pygccxml import declarations
     from pyplusplus import module_builder
     from pyplusplus import function_transformers as FT

     mb = module_builder.module_builder_t( ... )

     resource = mb.class_( 'resource_t' )
     resource.held_type = 'std::auto_ptr< %s >' % resource.decl_string
     do_smth = mb.free_fun( 'do_smth' )
     do_smth.add_transformation( FT.transfer_ownership( 0 ) )

What you see below is the relevant pieces of generated code:

  .. code-block:: C++

     namespace bp = boost::python;

     static void do_smth_4cf7cde5fca92efcdb8519f8c1a4bccd( std::auto_ptr< ::resource_t > r ){
      ::do_smth(r.release());
     }

     BOOST_PYTHON_MODULE(...){
         ...
         bp::def( "do_smth", &do_smth_4cf7cde5fca92efcdb8519f8c1a4bccd, ( bp::arg("r") ) );
     }

.. _`Py++` : ./../../../pyplusplus.html
.. _`Boost.Python`: http://www.boost.org/libs/python/doc/index.html
.. _`Python`: http://www.python.org
.. _`GCC-XML`: http://www.gccxml.org

