1<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN' 2'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'> 3<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'> 4<head> 5 <meta http-equiv='Content-Type' content='text/html; charset=utf-8'/> 6 <title>integrating boost exception in existing exception class hierarchies</title> 7 <link href='reno.css' type='text/css' rel='stylesheet'/> 8</head> 9<body> 10<div class="body-0"> 11<div class="body-1"> 12<div class="body-2"> 13<div> 14<div id="boost_logo"> 15<a href="http://www.boost.org"><img style="border:0" src="../../../boost.png" alt="Boost" width="277" height="86"/></a> 16</div> 17<h1>Boost Exception</h1> 18</div> 19<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. --> 20<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying --> 21<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> 22<div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h2>Integrating Boost Exception in Existing Exception Class Hierarchies</h2> 23</div> 24<p>Some exception hierarchies can not be modified to make boost::<span class="RenoLink"><a href="exception.html">exception</a></span> a base type. In this case, the <span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span> function template can be used to make exception objects derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> anyway. Here is an example:</p> 25<pre>#include <<span class="RenoLink"><a href="boost_exception_all_hpp.html">boost/exception/all.hpp</a></span>> 26#include <stdexcept> 27 28typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_min,size_t> std_range_min; 29typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_max,size_t> std_range_max; 30typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_index,size_t> std_range_index; 31 32template <class T> 33class 34my_container 35 { 36 public: 37 38 size_t size() const; 39 40 T const & 41 operator[]( size_t i ) const 42 { 43 if( i > size() ) 44 throw boost::<span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span>(std::range_error("Index out of range")) << 45 std_range_min(0) << 46 std_range_max(size()) << 47 std_range_index(i); 48 //.... 49 } 50 }; 51</pre> 52<p>The call to <span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span><T> gets us an object of <i>unspecified type</i> which is guaranteed to derive from both boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and T. This makes it possible to use <span class="RenoLink"><a href="exception_operator_shl.html">operator<<</a></span> to store additional information in the exception object. The exception can be intercepted as T &, so existing exception handling will not break. It can also be intercepted as boost::<span class="RenoLink"><a href="exception.html">exception</a></span> &, so that <span class="RenoLink"><a href="tutorial_transporting_data.html">more information can be added to the exception at a later time</a></span>.</p> 53</div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div> 54See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a> | <a href="motivation.html">Motivation</a></span> 55</div> 56<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. --> 57<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying --> 58<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> 59<div id="footer"> 60<p> 61<a class="logo" href="http://jigsaw.w3.org/css-validator/check/referer"><img class="logo_pic" src="valid-css.png" alt="Valid CSS" height="31" width="88"/></a> 62<a class="logo" href="http://validator.w3.org/check?uri=referer"><img class="logo_pic" src="valid-xhtml.png" alt="Valid XHTML 1.0" height="31" width="88"/></a> 63<small>Copyright (c) 2006-2009 by Emil Dotchevski and Reverge Studios, Inc.<br/> 64Distributed under the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</small> 65</p> 66</div> 67</div> 68</div> 69</div> 70</body> 71</html> 72
