<html> <head> <!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc --> <title>Wrappers</title> <link rel="stylesheet" href="theme/style.css" type="text/css"> <link rel="prev" href="templates.html"> <link rel="next" href="exporting_an_entire_header.html"> </head> <body> <table width="100%" height="48" border="0" cellspacing="2"> <tr> <td><img src="../../../../boost.png"> </td> <td width="85%"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Wrappers</b></font> </td> </tr> </table> <br> <table border="0"> <tr> <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> <td width="30"><a href="templates.html"><img src="theme/l_arr.gif" border="0"></a></td> <td width="20"><a href="exporting_an_entire_header.html"><img src="theme/r_arr.gif" border="0"></a></td> </tr> </table> <p> Suppose you have this function:</p> <code><pre> <span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>> </span><span class=identifier>names</span><span class=special>(); </span></pre></code> <p> But you don't want to <a href="../../doc/v2/faq.html#question2"> to export std::vector<std::string></a>, you want this function to return a python list of strings. <a href="../../index.html"> Boost.Python</a> has excellent support for things like that:</p> <code><pre> <span class=identifier>list </span><span class=identifier>names_wrapper</span><span class=special>() { </span><span class=identifier>list </span><span class=identifier>result</span><span class=special>; // </span><span class=identifier>call </span><span class=identifier>original </span><span class=identifier>function </span><span class=identifier>vector</span><span class=special><</span><span class=identifier>string</span><span class=special>> </span><span class=identifier>v </span><span class=special>= </span><span class=identifier>names</span><span class=special>(); // </span><span class=identifier>put </span><span class=identifier>all </span><span class=identifier>the </span><span class=identifier>strings </span><span class=identifier>inside </span><span class=identifier>the </span><span class=identifier>python </span><span class=identifier>list </span><span class=identifier>vector</span><span class=special><</span><span class=identifier>string</span><span class=special>>::</span><span class=identifier>iterator </span><span class=identifier>it</span><span class=special>; </span><span class=keyword>for </span><span class=special>(</span><span class=identifier>it </span><span class=special>= </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(); </span><span class=identifier>it </span><span class=special>!= </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>end</span><span class=special>(); ++</span><span class=identifier>it</span><span class=special>){ </span><span class=identifier>result</span><span class=special>.</span><span class=identifier>append</span><span class=special>(*</span><span class=identifier>it</span><span class=special>); } </span><span class=keyword>return </span><span class=identifier>result</span><span class=special>; } </span><span class=identifier>BOOST_PYTHON_MODULE</span><span class=special>(</span><span class=identifier>test</span><span class=special>) { </span><span class=identifier>def</span><span class=special>(</span><span class=string>"names"</span><span class=special>, &</span><span class=identifier>names_wrapper</span><span class=special>); } </span></pre></code> <p> Nice heh? Pyste supports this mechanism too. You declare the <tt>names_wrapper</tt> function in a header named "<tt>test_wrappers.h</tt>" and in the interface file:</p> <code><pre> <span class=identifier>Include</span><span class=special>(</span><span class=string>"test_wrappers.h"</span><span class=special>) </span><span class=identifier>names </span><span class=special>= </span><span class=identifier>Function</span><span class=special>(</span><span class=string>"names"</span><span class=special>, </span><span class=string>"test.h"</span><span class=special>) </span><span class=identifier>set_wrapper</span><span class=special>(</span><span class=identifier>names</span><span class=special>, </span><span class=string>"names_wrapper"</span><span class=special>) </span></pre></code> <p> You can optionally declare the function in the interface file itself:</p> <code><pre> <span class=identifier>names_wrapper </span><span class=special>= </span><span class=identifier>Wrapper</span><span class=special>(</span><span class=string>"names_wrapper"</span><span class=special>, </span><span class=string>""</span><span class=string>" list names_wrapper() { // code to call name() and convert the vector to a list... } "</span><span class=string>""</span><span class=special>) </span><span class=identifier>names </span><span class=special>= </span><span class=identifier>Function</span><span class=special>(</span><span class=string>"names"</span><span class=special>, </span><span class=string>"test.h"</span><span class=special>) </span><span class=identifier>set_wrapper</span><span class=special>(</span><span class=identifier>names</span><span class=special>, </span><span class=identifier>names_wrapper</span><span class=special>) </span></pre></code> <p> The same mechanism can be used with member functions too. Just remember that the first parameter of wrappers for member functions is a pointer to the class, as in:</p> <code><pre> <span class=keyword>struct </span><span class=identifier>C </span><span class=special>{ </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>> </span><span class=identifier>names</span><span class=special>(); } </span><span class=identifier>list </span><span class=identifier>names_wrapper</span><span class=special>(</span><span class=identifier>C</span><span class=special>* </span><span class=identifier>c</span><span class=special>) { // </span><span class=identifier>same </span><span class=identifier>as </span><span class=identifier>before</span><span class=special>, </span><span class=identifier>calling </span><span class=identifier>c</span><span class=special>-></span><span class=identifier>names</span><span class=special>() </span><span class=keyword>and </span><span class=identifier>converting </span><span class=identifier>result </span><span class=identifier>to </span><span class=identifier>a </span><span class=identifier>list </span><span class=special>} </span></pre></code> <p> And then in the interface file:</p> <code><pre> <span class=identifier>C </span><span class=special>= </span><span class=identifier>Class</span><span class=special>(</span><span class=string>"C"</span><span class=special>, </span><span class=string>"test.h"</span><span class=special>) </span><span class=identifier>set_wrapper</span><span class=special>(</span><span class=identifier>C</span><span class=special>.</span><span class=identifier>names</span><span class=special>, </span><span class=string>"names_wrapper"</span><span class=special>) </span></pre></code> <table width="80%" border="0" align="center"> <tr> <td class="note_box"> <img src="theme/note.gif"></img>Even though <a href="../../index.html"> Boost.Python</a> accepts either a pointer or a reference to the class in wrappers for member functions as the first parameter, Pyste expects them to be a <b>pointer</b>. Doing otherwise will prevent your code to compile when you set a wrapper for a virtual member function. </td> </tr> </table> <table border="0"> <tr> <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> <td width="30"><a href="templates.html"><img src="theme/l_arr.gif" border="0"></a></td> <td width="20"><a href="exporting_an_entire_header.html"><img src="theme/r_arr.gif" border="0"></a></td> </tr> </table> <br> <hr size="1"><p class="copyright">Copyright © 2003 Bruno da Silva de Oliveira<br>Copyright © 2002-2003 Joel de Guzman<br><br> <font size="2">Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) </font> </p> </body> </html>