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  26 <a name="boost.contract.destructor"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Function template destructor</span></h2>
  29 <p>boost::contract::destructor &#8212; Program contracts for destructors. </p>
  30 </div>
  31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  32 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../reference.html#header.boost.contract.destructor_hpp" title="Header &lt;boost/contract/destructor.hpp&gt;">boost/contract/destructor.hpp</a>&gt;
  33
  34 </span>
  35 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Class<span class="special">&gt;</span>
  36   <a class="link" href="specify__idm45394999245856.html" title="Class template specify_old_postcondition_except">specify_old_postcondition_except</a> <span class="identifier">destructor</span><span class="special">(</span><span class="identifier">Class</span> <span class="special">*</span> obj<span class="special">)</span><span class="special">;</span></pre></div>
  37 <div class="refsect1">
  38 <a name="idm45707995026416"></a><h2>Description</h2>
  39 <p>This is used to specify postconditions, exception guarantees, old value copies at body, and check class invariants for destructors (destructors cannot have preconditions, see  <a class="link" href="../../boost_contract/contract_programming_overview.html#boost_contract.contract_programming_overview.destructor_calls" title="Destructor Calls"> Destructor Calls</a>):</p>
  40 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span> <span class="special">{</span>
  41     <span class="keyword">friend</span> <span class="keyword">class</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">access</span><span class="special">;</span>
  42
  43     <span class="keyword">void</span> <span class="identifier">invariant</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">{</span> <span class="comment">// Optional (as for static and volatile).</span>
  44         <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  45         <span class="special">...</span>
  46     <span class="special">}</span>
  47
  48 <span class="keyword">public</span><span class="special">:</span>
  49     <span class="special">~</span><span class="identifier">u</span><span class="special">(</span><span class="special">)</span> <span class="special">{</span>
  50         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">old_ptr</span><span class="special">&lt;</span><span class="identifier">old_type</span><span class="special">&gt;</span> <span class="identifier">old_var</span><span class="special">;</span>
  51         <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">check</span> <span class="identifier">c</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">contract</span><span class="special">::</span><span class="identifier">destructor</span><span class="special">(</span><span class="keyword">this</span><span class="special">)</span>
  52             <span class="comment">// No `.precondition` (destructors have no preconditions).</span>
  53             <span class="special">.</span><span class="identifier">old</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  54                 <span class="identifier">old_var</span> <span class="special">=</span> <span class="identifier">BOOST_CONTRACT_OLDOF</span><span class="special">(</span><span class="identifier">old_expr</span><span class="special">)</span><span class="special">;</span>
  55                 <span class="special">...</span>
  56             <span class="special">}</span><span class="special">)</span>
  57             <span class="special">.</span><span class="identifier">postcondition</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  58                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  59                 <span class="special">...</span>
  60             <span class="special">}</span><span class="special">)</span>
  61             <span class="special">.</span><span class="identifier">except</span><span class="special">(</span><span class="special">[</span><span class="special">&amp;</span><span class="special">]</span> <span class="special">{</span> <span class="comment">// Optional.</span>
  62                 <span class="identifier">BOOST_CONTRACT_ASSERT</span><span class="special">(</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  63                 <span class="special">...</span>
  64             <span class="special">}</span><span class="special">)</span>
  65         <span class="special">;</span>
  66
  67         <span class="special">...</span> <span class="comment">// Destructor body.</span>
  68     <span class="special">}</span>
  69
  70     <span class="special">...</span>
  71 <span class="special">}</span><span class="special">;</span>
  72 </pre>
  73 <p>For optimization, this can be omitted for destructors that do not have postconditions and exception guarantees, within classes that have no invariants.</p>
  74 <p><span class="bold"><strong>See Also:</strong></span></p>
  75 <p> <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.destructors" title="Destructors"> Destructors</a></p>
  76 <p>
  77 </p>
  78 <p>
  79
  80
  81
  82 </p>
  83 <div class="variablelist"><table border="0" class="variablelist compact">
  84 <colgroup>
  85 <col align="left" valign="top">
  86 <col>
  87 </colgroup>
  88 <tbody>
  89 <tr>
  90 <td><p><span class="term">Parameters:</span></p></td>
  91 <td><div class="variablelist"><table border="0" class="variablelist compact">
  92 <colgroup>
  93 <col align="left" valign="top">
  94 <col>
  95 </colgroup>
  96 <tbody><tr>
  97 <td><p><span class="term"><code class="computeroutput">obj</code></span></p></td>
  98 <td><p>The object <code class="computeroutput">this</code> from the scope of the enclosing destructor declaring the contract. (Destructors check all class invariants, including static and volatile invariants, see <a class="link" href="../../boost_contract/tutorial.html#boost_contract.tutorial.class_invariants" title="Class Invariants">
  99             Class Invariants</a> and  <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.volatile_public_functions" title="Volatile Public Functions">
 100             Volatile Public Functions</a>).</p></td>
 101 </tr></tbody>
 102 </table></div></td>
 103 </tr>
 104 <tr>
 105 <td><p><span class="term">Template Parameters:</span></p></td>
 106 <td><div class="variablelist"><table border="0" class="variablelist compact">
 107 <colgroup>
 108 <col align="left" valign="top">
 109 <col>
 110 </colgroup>
 111 <tbody><tr>
 112 <td><p><span class="term"><code class="computeroutput">Class</code></span></p></td>
 113 <td><p>The type of the class containing the destructor declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)</p></td>
 114 </tr></tbody>
 115 </table></div></td>
 116 </tr>
 117 <tr>
 118 <td><p><span class="term">Returns:</span></p></td>
 119 <td><p>The result of this function must be assigned to a variable of type  <code class="computeroutput"><a class="link" href="check.html" title="Class check">boost::contract::check</a></code> declared explicitly (i.e., without using C++11 <code class="computeroutput">auto</code> declarations) and locally just before the code of the destructor body (otherwise this library will generate a run-time error, see <code class="computeroutput"><a class="link" href="../../BOOST_CO_idm45394999694064.html" title="Macro BOOST_CONTRACT_ON_MISSING_CHECK_DECL">BOOST_CONTRACT_ON_MISSING_CHECK_DECL</a></code>). </p></td>
 120 </tr>
 121 </tbody>
 122 </table></div>
 123 </div>
 124 </div>
 125 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 126 <td align="left"></td>
 127 <td align="right"><div class="copyright-footer">Copyright &#169; 2008-2019 Lorenzo Caminiti<p>
 128         Distributed under the Boost Software License, Version 1.0 (see accompanying
 129         file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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