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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Boost.Python - <boost/python/data_members.hpp></title>
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<h3><a href="../../../../index.htm"><img height="86" width="277"
alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3>
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<td valign="top">
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
<h2 align="center">Header
<boost/python/data_members.hpp></h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#functions">Functions</a></dt>
<dd>
<dl class="page-index">
<dt><a href="#make_getter-spec">make_getter</a></dt>
<dt><a href="#make_setter-spec">make_setter</a></dt>
</dl>
</dd>
<dt><a href="#examples">Example</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p><code><a href="#make_getter-spec">make_getter</a>()</code> and
<code><a href="#make_setter-spec">make_setter</a>()</code> are the
functions used internally by <code>class_<>::<a href=
"class.html#class_-spec-modifiers">def_readonly</a></code> and
<code>class_<>::<a href=
"class.html#class_-spec-modifiers">def_readwrite</a></code> to produce
Python callable objects which wrap C++ data members.</p>
<h2><a name="functions"></a>Functions</h2>
<pre>
<a name="make_getter-spec">template <class C, class D></a>
<a href="object.html#object-spec">object</a> make_getter(D C::*pm);
template <class C, class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_getter(D C::*pm, Policies const& policies);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
"CallPolicies.html">CallPolicies</a>.</dt>
<dt><b>Effects:</b> Creates a Python callable object which accepts a
single argument that can be converted <code>from_python</code> to
<code>C*</code>, and returns the corresponding member <code>D</code>
member of the <code>C</code> object, converted <code>to_python</code>.
If <code>policies</code> is supplied, it will be applied to the
function as described <a href="CallPolicies.html">here</a>. Otherwise,
the library attempts to determine whether <code>D</code> is a
user-defined class type, and if so uses <code><a href=
"return_internal_reference.html#return_internal_reference-spec">return_internal_reference</a><></code></dt>
<dt>for <code>Policies</code>. Note that this test may inappropriately
choose <code>return_internal_reference<></code> in some cases
when <code>D</code> is a smart pointer type. This is a known
defect.</dt>
<dt><b>Returns:</b> An instance of <a href=
"object.html#object-spec">object</a> which holds the new Python
callable object.</dt>
</dl>
<pre>
template <class D>
<a href="object.html#object-spec">object</a> make_getter(D const& d);
template <class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_getter(D const& d, Policies const& policies);
template <class D>
<a href="object.html#object-spec">object</a> make_getter(D const* p);
template <class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_getter(D const* p, Policies const& policies);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
"CallPolicies.html">CallPolicies</a>.</dt>
<dt><b>Effects:</b> Creates a Python callable object which accepts no
arguments and returns <code>d</code> or <code>*p</code>, converted
<code>to_python</code> on demand. If <code>policies</code> is supplied,
it will be applied to the function as described <a href=
"CallPolicies.html">here</a>. Otherwise, the library attempts to
determine whether <code>D</code> is a user-defined class type, and if
so uses <code><a href=
"reference_existing_object.html#reference_existing_object-spec">reference_existing_object</a></code></dt>
<dt>for <code>Policies</code>.</dt>
<dt><b>Returns:</b> An instance of <a href=
"object.html#object-spec">object</a> which holds the new Python
callable object.</dt>
</dl>
<pre>
<a name="make_setter-spec">template <class C, class D></a>
<a href="object.html#object-spec">object</a> make_setter(D C::*pm);
template <class C, class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_setter(D C::*pm, Policies const& policies);
</pre>
<dl class="function*-semantics">
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
"CallPolicies.html">CallPolicies</a>.</dt>
<dt><b>Effects:</b> Creates a Python callable object which, when called
from Python, expects two arguments which can be converted
<code>from_python</code> to <code>C*</code> and
<code>D const&</code>, respectively, and sets the
corresponding <code>D</code> member of the <code>C</code> object. If
<code>policies</code> is supplied, it will be applied to the function
as described <a href="CallPolicies.html">here</a>.</dt>
<dt><b>Returns:</b> An instance of <a href=
"object.html#object-spec">object</a> which holds the new Python
callable object.</dt>
</dl>
<pre>
template <class D>
<a href="object.html#object-spec">object</a> make_setter(D& d);
template <class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_setter(D& d, Policies const& policies);
template <class D>
<a href="object.html#object-spec">object</a> make_setter(D* p);
template <class D, class Policies>
<a href=
"object.html#object-spec">object</a> make_setter(D* p, Policies const& policies);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
"CallPolicies.html">CallPolicies</a>.</dt>
<dt><b>Effects:</b> Creates a Python callable object which accepts one
argument, which is converted from Python to <code>D const&</code>
and written into <code>d</code> or <code>*p</code>, respectively. If
<code>policies</code> is supplied, it will be applied to the function
as described <a href="CallPolicies.html">here</a>.</dt>
<dt><b>Returns:</b> An instance of <a href=
"object.html#object-spec">object</a> which holds the new Python
callable object.</dt>
</dl>
<h2><a name="examples"></a>Example</h2>
<p>The code below uses make_getter and make_setter to expose a data
member as functions:</p>
<pre>
#include <boost/python/data_members.hpp>
#include <boost/python/module.hpp>
#include <boost/python/class.hpp>
struct X
{
X(int x) : y(x) {}
int y;
};
using namespace boost::python;
BOOST_PYTHON_MODULE_INIT(data_members_example)
{
class_<X>("X", init<int>())
.def("get", make_getter(&X::y))
.def("set", make_setter(&X::y))
;
}
</pre>
It can be used this way in Python:
<pre>
>>> from data_members_example import *
>>> x = X(1)
>>> x.get()
1
>>> x.set(2)
>>> x.get()
2
</pre>
<p>
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
5 August, 2003 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>© Copyright <a href=
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p>
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