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- register_ptr_to_python addition
[SVN r18880]
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‎doc/v2/reference.html‎

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@@ -973,6 +973,22 @@ <h2><a name="type_conversion">To/From Python Type Conversion</a></h2>
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</dd>
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</dl>
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</dd>
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<dt><a href="register_ptr_to_python.html">register_ptr_to_python.hpp</a></dt>
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<dd>
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<dl class="index">
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<dt><a href="register_ptr_to_python.html#functions">Functions</a></dt>
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<dd>
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<dl class="index">
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<dt><a href=
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"register_ptr_to_python.html#register_ptr_to_python-spec">register_ptr_to_python</a></dt>
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</dl>
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</dd>
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</dl>
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</dd>
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</dl>
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<h2><a name="utility">Utility and Infrastructure</a></h2>

‎doc/v2/register_ptr_to_python.html‎

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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../boost.css">
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<title>Boost.Python - &lt;register_ptr_to_python.hpp&gt;</title>
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</head>
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<body link="#0000ff" vlink="#800080">
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<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
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"header">
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<tr>
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<td valign="top" width="300">
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<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
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"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
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</td>
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<td valign="top">
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<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
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<h2 align="center">Header &lt;register_ptr_to_python.hpp&gt;</h2>
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</td>
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</tr>
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</table>
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<hr>
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<h2>Contents</h2>
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<dl class="page-index">
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<dt><a href="#introduction">Introduction</a></dt>
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<dt><a href="#functions">Functions</a></dt>
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<dl class="page-index">
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<dt><a href="#register_ptr_to_python-spec">register_ptr_to_python</a></dt>
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</dl>
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<dt><a href="#examples">Example(s)</a></dt>
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</dl>
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<hr>
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<h2><a name="introduction"></a>Introduction</h2>
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<p>
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<code>&lt;boost/python/converter/register_ptr_to_python.hpp&gt;</code>
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supplies <code>register_ptr_to_python</code>, a function template
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which registers a conversion for smart pointers to Python. The
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resulting Python object holds a copy of the converted smart pointer,
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but behaves as though it were a wrapped copy of the pointee. If
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the pointee type has virtual functions and the class representing
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its dynamic (most-derived) type has been wrapped, the Python object
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will be an instance of the wrapper for the most-derived type. More than
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one smart pointer type for a pointee's class can be registered.
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</p>
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<p>
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Note that in order to convert a Python <code>X</code> object to a
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<code>smart_ptr&lt;X&gt;&amp;</code> (non-const reference), the embedded C++
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object must be held by <code>smart_ptr&lt;X&gt;</code>, and that when wrapped
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objects are created by calling the constructor from Python, how they are held
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is determined by the <code>HeldType</code> parameter to class_&lt;...&gt;
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instances.
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</p>
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<h2><a name="functions"></a>Functions</h2>
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<pre>
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<a name="register_ptr_to_python-spec">template &lt;class P&gt;
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void register_ptr_to_python()
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>P</code> is the type of the smart pointer,
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for example <code>smart_ptr&lt;X&gt;</code>.
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</dt>
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<dt><b>Effects:</b> Allows conversions to-python of <code>smart_ptr&lt;X&gt;</code>
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instances.
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</dt>
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</dl>
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<h2><a name="examples"></a>Example(s)</h2>
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<h3>C++ Wrapper Code</h3>
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Here is an example of a module that contains a class <code>A</code> with
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virtual functions and some functions that work with
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<code>boost::shared_ptr&lt;A&gt;</code>.
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<pre>
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struct A
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{
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virtual int f() { return 0; }
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};
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shared_ptr&lt;A&gt; New() { return shared_ptr&lt;A&gt;( new A() ); }
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int Ok( const shared_ptr&lt;A&gt;&amp; a ) { return a-&gt;f(); }
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int Fail( shared_ptr&lt;A&gt;&amp; a ) { return a-&gt;f(); }
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struct A_Wrapper: A
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{
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A_Wrapper(PyObject* self_): self(self_) {}
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int f() { return call_method&lt;int&gt;(self, "f"); }
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int default_f() { return A::f(); }
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PyObject* self;
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};
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BOOST_PYTHON_MODULE(register_ptr)
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{
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class_&lt;A, A_Wrapper&gt;("A")
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.def("f", &amp;A::f, &amp;A_Wrapper::default_f)
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;
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def("New", &amp;New);
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def("Ok", &amp;Call);
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def("Fail", &amp;Fail);
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register_ptr_to_python&lt; shared_ptr&lt;A&gt; &gt;();
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}
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</pre>
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<h3>Python Code</h3>
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<pre>
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&gt;&gt;&gt; from register_ptr import *
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&gt;&gt;&gt; a = A()
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&gt;&gt;&gt; Ok(a) # ok, passed as shared_ptr&lt;A&gt;
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0
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&gt;&gt;&gt; Fail(a) # passed as shared_ptr&lt;A&gt;&amp;, and was created in Python!
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Traceback (most recent call last):
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File "&lt;stdin&gt;", line 1, in ?
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TypeError: bad argument type for built-in operation
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&gt;&gt;&gt;
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&gt;&gt;&gt; na = New() # now "na" is actually a shared_ptr&lt;A&gt;
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&gt;&gt;&gt; Ok(a)
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0
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&gt;&gt;&gt; Fail(a)
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0
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&gt;&gt;&gt;
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</pre>
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If <code>shared_ptr&lt;A&gt;</code> is registered as follows:
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<pre>
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class_&lt;A, A_Wrapper, shared_ptr&lt;A&gt; &gt;("A")
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.def("f", &amp;A::f, &amp;A_Wrapper::default_f)
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;
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</pre>
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There will be an error when trying to convert <code>shared_ptr&lt;A&gt;</code> to
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<code>shared_ptr&lt;A_Wrapper&gt;</code>:
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<pre>
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&gt;&gt;&gt; a = New()
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Traceback (most recent call last):
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File "&lt;stdin&gt;", line 1, in ?
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TypeError: No to_python (by-value) converter found for C++ type: class boost::shared_ptr&lt;struct A&gt;
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&gt;&gt;&gt;
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</pre>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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24 Jun, 2003
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<p><i>&copy; Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
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2002. All Rights Reserved.</i></p>
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</body>
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</html>
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‎include/boost/python.hpp‎

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# include <boost/python/tuple.hpp>
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# include <boost/python/type_id.hpp>
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# include <boost/python/with_custodian_and_ward.hpp>
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# include <boost/python/converter/register_ptr_to_python.hpp>
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#endif // PYTHON_DWA2002810_HPP

‎include/boost/python/converter/register_ptr_to_python.hpp‎

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// Copyright David Abrahams 2002. Permission to copy, use,
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// modify, sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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#ifndef REGISTER_PTR_TO_PYTHON_HPP
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#define REGISTER_PTR_TO_PYTHON_HPP
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#include <boost/python/pointee.hpp>
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#include <boost/python/object.hpp>
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namespace boost { namespace python {
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template <class P>
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void register_ptr_to_python(P* = 0)
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{
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typedef typename boost::python::pointee<P>::type X;
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objects::class_value_wrapper<
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P
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, objects::make_ptr_instance<
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X
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, objects::pointer_holder<P,X>
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>
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>();
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}
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}} // namespace boost::python
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#endif // REGISTER_PTR_TO_PYTHON_HPP
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‎test/register_ptr.cpp‎

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#include <boost/python.hpp>
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#include <boost/shared_ptr.hpp>
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using namespace boost;
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using namespace python;
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struct A
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{
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virtual int f() { return 0; }
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};
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shared_ptr<A> New() { return shared_ptr<A>( new A() ); }
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int Call( const shared_ptr<A> & a )
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{
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return a->f();
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}
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int Fail( shared_ptr<A> & a )
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{
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return a->f();
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}
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struct A_Wrapper: A
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{
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A_Wrapper(PyObject* self_): self(self_) {}
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A_Wrapper(PyObject* self_, const A& a): self(self_), A(a) {}
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int f()
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{
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return call_method<int>(self, "f");
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}
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int default_f()
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{
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return A::f();
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}
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PyObject* self;
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};
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BOOST_PYTHON_MODULE(register_ptr)
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{
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class_<A, A_Wrapper>("A")
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.def("f", &A::f, &A_Wrapper::default_f)
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;
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register_ptr_to_python< shared_ptr<A> >();
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def("New", &New);
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def("Call", &Call);
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def("Fail", &Fail);
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}

‎test/register_ptr_test.py‎

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import unittest
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from register_ptr import *
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class RegisterPtrTest(unittest.TestCase):
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def testIt(self):
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class B(A):
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def f(self):
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return 10
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a = New() # this must work
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b = B()
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self.assertEqual(Call(a), 0)
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self.assertEqual(Call(b), 10)
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def fails():
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Fail(A())
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self.assertRaises(TypeError, fails)
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self.assertEqual(Fail(a), 0) # ok, since a is held by shared_ptr
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if __name__ == '__main__':
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unittest.main()

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