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<title>Why is my automatic to-python conversion not being found?</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="faq.why_is_my_automatic_to_python_co"></a><a class="link" href="why_is_my_automatic_to_python_co.html" title="Why is my automatic to-python conversion not being found?">Why is my automatic
      to-python conversion not being found?</a>
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<p>
        <span class="emphasis"><em>Niall Douglas provides these notes:</em></span>
      </p>
<p>
        If you define custom converters similar to the ones shown above the <code class="computeroutput"><span class="identifier">def_readonly</span><span class="special">()</span></code>
        and <code class="computeroutput"><span class="identifier">def_readwrite</span><span class="special">()</span></code>
        member functions provided by <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">::</span><span class="identifier">class_</span></code>
        for direct access to your member data will not work as expected. This is
        because <code class="computeroutput"><span class="identifier">def_readonly</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">)</span></code> is equivalent to:
      </p>
<pre class="programlisting"><span class="special">.</span><span class="identifier">add_property</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,</span> <span class="identifier">make_getter</span><span class="special">(&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">,</span> <span class="identifier">return_internal_reference</span><span class="special">()))</span>
</pre>
<p>
        Similarly, <code class="computeroutput"><span class="identifier">def_readwrite</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">)</span></code>
        is equivalent to:
      </p>
<pre class="programlisting"><span class="special">.</span><span class="identifier">add_property</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,</span> <span class="identifier">make_getter</span><span class="special">(&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">,</span> <span class="identifier">return_internal_reference</span><span class="special">()),</span>
                   <span class="identifier">make_setter</span><span class="special">(&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">,</span> <span class="identifier">return_internal_reference</span><span class="special">())</span>
</pre>
<p>
        In order to define return value policies compatible with the custom conversions
        replace <code class="computeroutput"><span class="identifier">def_readonly</span><span class="special">()</span></code>
        and <code class="computeroutput"><span class="identifier">def_readwrite</span><span class="special">()</span></code>
        by <code class="computeroutput"><span class="identifier">add_property</span><span class="special">()</span></code>.
        E.g.:
      </p>
<pre class="programlisting"><span class="special">.</span><span class="identifier">add_property</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,</span> <span class="identifier">make_getter</span><span class="special">(&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">,</span> <span class="identifier">return_value_policy</span><span class="special">&lt;</span><span class="identifier">return_by_value</span><span class="special">&gt;()),</span>
                   <span class="identifier">make_setter</span><span class="special">(&amp;</span><span class="identifier">foo</span><span class="special">::</span><span class="identifier">bar</span><span class="special">,</span> <span class="identifier">return_value_policy</span><span class="special">&lt;</span><span class="identifier">return_by_value</span><span class="special">&gt;()))</span>
</pre>
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