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<title>Boost.Python - <boost/python/scope.hpp></title>
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<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
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<td valign="top" width="300">
<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/scope.hpp></h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dd>
<dl class="page-index">
<dt><a href="#scope-spec">Class <code>scope</code></a></dt>
<dd>
<dl class="page-index">
<dt><a href="#scope-spec-synopsis">Class <code>scope</code>
synopsis</a></dt>
<dt><a href="#scope-spec-ctors">Class <code>scope</code>
constructors and destructor</a></dt>
</dl>
</dd>
</dl>
</dd>
<dt><a href="#examples">Example</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Defines facilities for querying and controlling the Python scope
(namespace) which will contain new wrapped classes and functions.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="scope-spec"></a>Class <code>scope</code></h3>
<p>The <code>scope</code> class has an associated global Python
object which controls the Python namespace in which new extension
classes and wrapped functions will be defined as
attributes. Default-constructing a new <code>scope</code> object
binds it to the associated global Python object. Constructing a
<code>scope</code> object with an argument changes the associated
global Python object to the one held by the argument, until the
lifetime of the <code>scope</code> object ends, at which time the
associated global Python object reverts to what it was before the
<code>scope</code> object was constructed.</p>
<h4><a name="scope-spec-synopsis"></a>Class <code>scope</code>
synopsis</h4>
<pre>
namespace boost { namespace python
{
class scope : public <a href=
"object.html#object-spec">object</a>
{
public:
scope(scope const&);
scope(object const&);
scope();
~scope()
private:
void operator=(scope const&);
};
}}
</pre>
<h4><a name="scope-spec-ctors"></a>Class <code>scope</code> constructors
and destructor</h4>
<pre>
explicit scope(scope const& x);
explicit scope(object const& x);
</pre>
Stores a reference to the current associated scope object, and sets the
associated scope object to the one referred to by <code>x.ptr()</code>.
The <code>object</code> base class is initialized with <code>x</code>.
<pre>
scope();
</pre>
Stores a reference to the current associated scope object. The
<code>object</code> base class is initialized with the current associated
scope object. Outside any module initialization function, the current
associated Python object is <code>None</code>.
<pre>
~scope()
</pre>
Sets the current associated Python object to the stored object.
<h2><a name="examples"></a>Example</h2>
The following example shows how scope setting can be used to define
nested classes.
<p>C++ Module definition:</p>
<pre>
#include <boost/python/class.hpp>
#include <boost/python/scope.hpp>
using namespace boost::python;
struct X
{
void f();
struct Y { int g() { return 42; } };
};
BOOST_PYTHON_MODULE(nested)
{
// add some constants to the current (module) scope
scope().attr("yes") = 1;
scope().attr("no") = 0;
// Change the current scope
scope outer
= class_<X>("X")
.def("f", &X::f)
;
// Define a class Y in the current scope, X
class_<Y>("Y")
.def("g", &Y::g)
;
}
</pre>
Interactive Python:
<pre>
>>> import nested
>>> nested.yes
1
>>> y = nested.X.Y()
>>> y.g()
42
</pre>
<p>Revised 09 October, 2002</p>
<p><i>© Copyright <a href=
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p>
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