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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>
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