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| <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Wrappers</b></font> |
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| <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> |
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| <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. |
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| <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> |
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