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diff --git a/libs/python/doc/v2/ObjectWrapper.html b/libs/python/doc/v2/ObjectWrapper.html new file mode 100644 index 0000000000..7962e69fa5 --- /dev/null +++ b/libs/python/doc/v2/ObjectWrapper.html @@ -0,0 +1,153 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> + +<!-- Copyright David Abrahams 2006. 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) --> +<html> + <head> + <meta name="generator" content= + "HTML Tidy for Windows (vers 1st August 2002), see www.w3.org"> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <link rel="stylesheet" type="text/css" href="../boost.css"> + + <title>Boost.Python - ObjectWrapper Concept</title> + </head> + + <body link="#0000ff" vlink="#800080"> + <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= + "header"> + <tr> + <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> + </td> + + <td valign="top"> + <h1 align="center"><a href="../index.html">Boost.Python</a></h1> + + <h2 align="center">ObjectWrapper and TypeWrapper Concepts</h2> + </td> + </tr> + </table> + <hr> + + <dl class="page-index"> + <dt><a href="#introduction">Introduction</a></dt> + + <dt><a href="#concept-requirements">Concept Requirements</a></dt> + + <dd> + <dl class="page-index"> + <dt><a href="#ObjectWrapper-concept">ObjectWrapper Concept</a></dt> + + <dt><a href="#TypeWrapper-concept">TypeWrapper Concept</a></dt> + </dl> + </dd> + + <dt><a href="#caveat">Caveat</a></dt> + </dl> + + <h2><a name="introduction"></a>Introduction</h2> + + <p>This page defines two concepts used to describe classes which manage a + Python objects, and which are intended to support usage with a + Python-like syntax.</p> + + <h2><a name="concept-requirements"></a>Concept Requirements</h2> + + <h3><a name="ObjectWrapper-concept"></a>ObjectWrapper Concept</h3> + Models of the ObjectWrapper concept have <a href= + "object.html#object-spec">object</a> as a publicly-accessible base class, + and are used to supply special construction behavior and/or additional + convenient functionality through (often templated) member functions. + Except when the return type <code>R</code> is itself an <a href= + "#TypeWrapper-concept">TypeWrapper</a>, a member function invocation of + the form +<pre> +x.<i>some_function</i>(<i>a<small>1</small>, a<small>2</small>,...a<small>n</small></i>) +</pre> + always has semantics equivalent to: +<pre> +<a href= +"extract.html#extract-spec">extract</a><R>(x.attr("<i>some_function</i>")(<a + href= +"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a +href= +"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a +href="object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>)))() +</pre> + When the <code>R</code> is an <a href= + "#TypeWrapper-concept">TypeWrapper</a>, the result type may be + constructed by taking direct posession of: +<pre> +x.attr("<i>some_function</i>")(<a href= +"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a + href= +"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a + href= +"object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>)).ptr() +</pre> + [see <a href="#caveat">caveat</a> below] + + <h3><a name="TypeWrapper-concept"></a>TypeWrapper Concept</h3> + TypeWrapper is a refinement of ObjectWrapper which is associated with a + particular Python type <code>X</code>. For a given TypeWrapper + <code>T</code>, a valid constructor expression +<pre> +T(<i>a<small>1</small>, a<small>2</small>,...a<small>n</small></i>) +</pre> + builds a new <code>T</code> object managing the result of invoking + <code>X</code> with arguments corresponding to +<pre> +<a href= +"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a + href= +"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a + href= +"object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>) +</pre> + +When used as arguments to wrapped C++ functions, or as the template +parameter to <code><a +href="extract.html#extract-spec">extract</a><></code>, only +instances of the associated Python type will be considered a match. + + <h3><a name="caveat">Caveat</a></h3> + The upshot of the special member function invocation rules when the + return type is a TypeWrapper is that it is possible for the returned + object to manage a Python object of an inappropriate type. This is not + usually a serious problem; the worst-case result is that errors will be + detected at runtime a little later than they might otherwise be. For an + example of how this can occur, note that the <code><a href= + "dict.html#dict-spec">dict</a></code> member function <code>items</code> + returns an object of type <code><a href= + "list.html#list-spec">list</a></code>. Now suppose the user defines this + <code>dict</code> subclass in Python: +<pre> +>>> class mydict(dict): +... def items(self): +... return tuple(dict.items(self)) # return a tuple +</pre> + Since an instance of <code>mydict</code> is also an instance of + <code>dict</code>, when used as an argument to a wrapped C++ function, + <code><a href="dict.html#dict-spec">boost::python::dict</a></code> can + accept objects of Python type <code>mydict</code>. Invoking + <code>items()</code> on this object can result in an instance of <code><a + href="list.html#list-spec">boost::python::list</a></code> which actually + holds a Python tuple. Subsequent attempts to use list methods (e.g. + <code>append</code>, or any other mutating operation) on this object will + raise the same exception that would occur if you tried to do it from + Python. + <hr> + + <p>Revised + <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> + 13 November, 2002 + <!--webbot bot="Timestamp" endspan i-checksum="39359" --> + </p> + + <p><i>© Copyright <a href= + "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> + </body> +</html> + |