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<title>libsigc++: sigc::volatile_limit_reference< T_type, I_derives_trackable > Class Template Reference</title>
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<div id="projectname">libsigc++
 <span id="projectnumber">2.10.0</span>
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<li class="navelem"><a class="el" href="namespacesigc.html">sigc</a></li><li class="navelem"><a class="el" href="classsigc_1_1volatile__limit__reference.html">volatile_limit_reference</a></li> </ul>
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<div class="title">sigc::volatile_limit_reference< T_type, I_derives_trackable > Class Template Reference</div> </div>
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<p>A volatile_limit_reference<Foo> object stores a reference (Foo&), but make sure that, if Foo inherits from <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a>, then <a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404" title="This function performs a functor on each of the targets of a functor. ">visit_each<>()</a> will "limit" itself to the <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a> reference instead of the derived reference.
<a href="classsigc_1_1volatile__limit__reference.html#details">More...</a></p>
<p><code>#include <sigc++/limit_reference.h></code></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>
Public Member Functions</h2></td></tr>
<tr class="memitem:acb3e6e1ecc628343f94faae718b58066"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classsigc_1_1volatile__limit__reference.html#acb3e6e1ecc628343f94faae718b58066">volatile_limit_reference</a> (T_type& _A_target)</td></tr>
<tr class="memdesc:acb3e6e1ecc628343f94faae718b58066"><td class="mdescLeft"> </td><td class="mdescRight">Constructor. <a href="#acb3e6e1ecc628343f94faae718b58066">More...</a><br /></td></tr>
<tr class="separator:acb3e6e1ecc628343f94faae718b58066"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a932be0a7adce8fac57f269d551e271a3"><td class="memItemLeft" align="right" valign="top">volatile T_type& </td><td class="memItemRight" valign="bottom"><a class="el" href="classsigc_1_1volatile__limit__reference.html#a932be0a7adce8fac57f269d551e271a3">invoke</a> () const </td></tr>
<tr class="memdesc:a932be0a7adce8fac57f269d551e271a3"><td class="mdescLeft"> </td><td class="mdescRight">Retrieve the reference. <a href="#a932be0a7adce8fac57f269d551e271a3">More...</a><br /></td></tr>
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<tr class="memitem:a14357ecc1a8e064d5f5531ce82542e74"><td class="memItemLeft" align="right" valign="top">const T_type& </td><td class="memItemRight" valign="bottom"><a class="el" href="classsigc_1_1volatile__limit__reference.html#a14357ecc1a8e064d5f5531ce82542e74">visit</a> () const </td></tr>
<tr class="memdesc:a14357ecc1a8e064d5f5531ce82542e74"><td class="mdescLeft"> </td><td class="mdescRight">Retrieve the entity to visit for <a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404" title="This function performs a functor on each of the targets of a functor. ">visit_each()</a>. <a href="#a14357ecc1a8e064d5f5531ce82542e74">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><h3>template<class T_type, bool I_derives_trackable = std::is_base_of<trackable, T_type>::value><br />
class sigc::volatile_limit_reference< T_type, I_derives_trackable ></h3>
<p>A volatile_limit_reference<Foo> object stores a reference (Foo&), but make sure that, if Foo inherits from <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a>, then <a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404" title="This function performs a functor on each of the targets of a functor. ">visit_each<>()</a> will "limit" itself to the <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a> reference instead of the derived reference. </p>
<p>This avoids use of a reference to the derived type when the derived destructor has run. That can be a problem when using virtual inheritance.</p>
<p>If Foo inherits from trackable then both the derived reference and the <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a> reference are stored, so we can later retrieve the <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a> reference without doing an implicit conversion. To retrieve the derived reference (so that you invoke methods or members of it), use <a class="el" href="classsigc_1_1volatile__limit__reference.html#a932be0a7adce8fac57f269d551e271a3" title="Retrieve the reference. ">invoke()</a>. To retrieve the trackable reference (so that you can call <a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404" title="This function performs a functor on each of the targets of a functor. ">visit_each()</a> on it), you use <a class="el" href="classsigc_1_1volatile__limit__reference.html#a14357ecc1a8e064d5f5531ce82542e74" title="Retrieve the entity to visit for visit_each(). ">visit()</a>.</p>
<p>If Foo does not inherit from <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a> then <a class="el" href="classsigc_1_1volatile__limit__reference.html#a932be0a7adce8fac57f269d551e271a3" title="Retrieve the reference. ">invoke()</a> and <a class="el" href="classsigc_1_1volatile__limit__reference.html#a14357ecc1a8e064d5f5531ce82542e74" title="Retrieve the entity to visit for visit_each(). ">visit()</a> just return the derived reference.</p>
<p>This is used for bound (<a class="el" href="group__bind.html#ga2f099bc6056b32f2a58134ba8537c6f4" title="Creates an adaptor of type sigc::bind_functor which binds the passed argument to the passed functor...">sigc::bind</a>) slot parameters (via <a class="el" href="classsigc_1_1bound__argument.html" title="A bound_argument<Foo> object stores a bound (for instance, with sigc::bind(), or sigc::bind_return())...">bound_argument</a>), bound return values, and, with <a class="el" href="group__mem__fun.html#gadf6b6d22c503b439019f0a2e77352419" title="Creates a functor of type sigc::mem_functor0 which wraps a method. ">mem_fun()</a>, the reference to the handling object.</p>
<ul>
<li><em>T_type</em> The type of the reference. </li>
</ul>
</div><h2 class="groupheader">Constructor & Destructor Documentation</h2>
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template <class T_type, bool I_derives_trackable = std::is_base_of<trackable, T_type>::value> </div>
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<td class="memname"><a class="el" href="classsigc_1_1volatile__limit__reference.html">sigc::volatile_limit_reference</a>< T_type, I_derives_trackable >::<a class="el" href="classsigc_1_1volatile__limit__reference.html">volatile_limit_reference</a> </td>
<td>(</td>
<td class="paramtype">T_type & </td>
<td class="paramname"><em>_A_target</em></td><td>)</td>
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<p>Constructor. </p>
<dl class="params"><dt>Parameters</dt><dd>
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<tr><td class="paramname">_A_target</td><td>The reference to limit. </td></tr>
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<h2 class="groupheader">Member Function Documentation</h2>
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template <class T_type, bool I_derives_trackable = std::is_base_of<trackable, T_type>::value> </div>
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<td class="memname">volatile T_type& <a class="el" href="classsigc_1_1volatile__limit__reference.html">sigc::volatile_limit_reference</a>< T_type, I_derives_trackable >::invoke </td>
<td>(</td>
<td class="paramname"></td><td>)</td>
<td> const</td>
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<p>Retrieve the reference. </p>
<p>This is always a reference to the derived instance. </p><dl class="section return"><dt>Returns</dt><dd>The reference. </dd></dl>
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template <class T_type, bool I_derives_trackable = std::is_base_of<trackable, T_type>::value> </div>
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<td class="memname">const T_type& <a class="el" href="classsigc_1_1volatile__limit__reference.html">sigc::volatile_limit_reference</a>< T_type, I_derives_trackable >::visit </td>
<td>(</td>
<td class="paramname"></td><td>)</td>
<td> const</td>
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<p>Retrieve the entity to visit for <a class="el" href="group__sigcfunctors.html#ga64cb7832acc1e58efb5ffe0b4f5e9404" title="This function performs a functor on each of the targets of a functor. ">visit_each()</a>. </p>
<p>Depending on the template specialization, this is either a derived reference, or <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a>& if T_type derives from <a class="el" href="structsigc_1_1trackable.html" title="Base class for objects with auto-disconnection. ">sigc::trackable</a>. </p><dl class="section return"><dt>Returns</dt><dd>The reference. </dd></dl>
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