exception/doc/using_enable_error_info.html

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<h1>Boost Exception</h1>
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<div class="RenoIncludeDIV"><h2>Integrating Boost Exception in Existing Exception Class Hierarchies</h2>
<p>Some exception hierarchies can not be modified to make <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> a base type. For this case, the <tt><span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span>()</tt> function template can be used to make exception objects derive from <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> anyway. Here is an example:</p>
<pre>#include &lt;<span class="RenoLink"><a href="exception_hpp.html">boost/exception.hpp</a></span>&gt;
#include &lt;stdexcept&gt;

typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;struct tag_std_range_min,size_t&gt; std_range_min;
typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;struct tag_std_range_max,size_t&gt; std_range_max;
typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;struct tag_std_range_index,size_t&gt; std_range_index;

template &lt;class T&gt;
class
my_container
    {
    public:

    size_t size() const;

    T const &amp;
    operator[]( size_t i ) const
        {
        if( i &gt; size() )
            throw boost::<span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span>(std::range_error("Index out of range")) &lt;&lt;
                std_range_min(0) &lt;&lt;
                std_range_max(size()) &lt;&lt;
                std_range_index(i);
        //....
        }
    };
</pre>
<p><tt><span class="RenoLink"><a href="enable_error_info.html">Enable_error_info</a></span>&lt;T&gt;</tt> returns an object of <i>unspecified type</i> which is guaranteed to derive from both <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> and <tt>T</tt>. This makes it possible to use <tt><span class="RenoLink"><a href="operator_shl_exception.html">operator&lt;&lt;</a></span>()</tt> to store additional information in the exception object. The exception can be intercepted as <tt>T &amp;</tt>, therefore existing exception handling will not break. It can also be intercepted as <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span> &amp;</tt>, so that <span class="RenoLink"><a href="transporting_data.html">more information can be added to the exception at a later time</a></span>.</p>
</div><h3>See also:</h3>
<div class="RenoPageList"><a href="boost-exception.html">Boost Exception<br/>
</a></div>
<!-- Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc. -->
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boost exception [SVN r43485] 2008-03-04 01:41:17 +00:00			`<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'`
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			`<meta http-equiv='Content-Type' content='text/html; charset=utf-8'/>`
			`<title>Tutorial: Integrating Boost Exception in Existing Exception Class Hierarchies</title>`
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minor documentation fixes. [SVN r44476] 2008-04-16 22:55:19 +00:00			`<!-- Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc. -->`
			`<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->`
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boost exception [SVN r43485] 2008-03-04 01:41:17 +00:00			`<div class="RenoIncludeDIV"><h2>Integrating Boost Exception in Existing Exception Class Hierarchies</h2>`
			`<p>Some exception hierarchies can not be modified to make <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> a base type. For this case, the <tt><span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span>()</tt> function template can be used to make exception objects derive from <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> anyway. Here is an example:</p>`
			`<pre>#include <<span class="RenoLink"><a href="exception_hpp.html">boost/exception.hpp</a></span>>`
			`#include <stdexcept>`

			`typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_min,size_t> std_range_min;`
			`typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_max,size_t> std_range_max;`
			`typedef boost::<span class="RenoLink"><a href="error_info.html">error_info</a></span><struct tag_std_range_index,size_t> std_range_index;`

			`template <class T>`
			`class`
			`my_container`
			`{`
			`public:`

			`size_t size() const;`

			`T const &`
			`operator[]( size_t i ) const`
			`{`
			`if( i > size() )`
			`throw boost::<span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span>(std::range_error("Index out of range")) <<`
			`std_range_min(0) <<`
			`std_range_max(size()) <<`
			`std_range_index(i);`
			`//....`
			`}`
			`};`
			`</pre>`
			<p><tt><span class="RenoLink"><a href="enable_error_info.html">Enable_error_info</a></span><T></tt> returns an object of <i>unspecified type</i> which is guaranteed to derive from both <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> and <tt>T</tt>. This makes it possible to use <tt><span class="RenoLink"><a href="operator_shl_exception.html">operator<<</a></span>()</tt> to store additional information in the exception object. The exception can be intercepted as <tt>T &</tt>, therefore existing exception handling will not break. It can also be intercepted as <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span> &</tt>, so that <span class="RenoLink"><a href="transporting_data.html">more information can be added to the exception at a later time</a></span>.</p>
			`</div><h3>See also:</h3>`
			`<div class="RenoPageList"><a href="boost-exception.html">Boost Exception<br/>`
			`</a></div>`
minor documentation fixes. [SVN r44476] 2008-04-16 22:55:19 +00:00			`<!-- Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc. -->`
			`<!-- 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) -->`
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