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<title>defer (1 of 3 overloads)</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.defer.overload1"></a><a class="link" href="overload1.html" title="defer (1 of 3 overloads)">defer (1 of 3 overloads)</a>
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<p>
Submits a completion token or function object for execution.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">typename</span> <a class="link" href="../NullaryToken.html" title="Nullary token requirements">NullaryToken</a><span class="special">&gt;</span>
<a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> <span class="identifier">defer</span><span class="special">(</span>
<span class="identifier">NullaryToken</span> <span class="special">&amp;&amp;</span> <span class="identifier">token</span><span class="special">);</span>
</pre>
<p>
This function submits an object for execution using the object's associated
executor. The function object is queued for execution, and is never called
from the current thread prior to returning from <code class="computeroutput"><span class="identifier">defer</span><span class="special">()</span></code>.
</p>
<p>
The use of <code class="computeroutput"><span class="identifier">defer</span><span class="special">()</span></code>,
rather than <a class="link" href="../post.html" title="post"><code class="computeroutput"><span class="identifier">post</span></code></a>,
indicates the caller's preference that the executor defer the queueing
of the function object. This may allow the executor to optimise queueing
for cases when the function object represents a continuation of the current
call context.
</p>
<h6>
<a name="asio.reference.defer.overload1.h0"></a>
<span><a name="asio.reference.defer.overload1.parameters"></a></span><a class="link" href="overload1.html#asio.reference.defer.overload1.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">token</span></dt>
<dd>
<p>
The <a class="link" href="../../overview/model/completion_tokens.html" title="Completion Tokens">completion
token</a> that will be used to produce a completion handler. The
function signature of the completion handler must be:
</p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">();</span>
</pre>
</dd>
</dl>
</div>
<h6>
<a name="asio.reference.defer.overload1.h1"></a>
<span><a name="asio.reference.defer.overload1.return_value"></a></span><a class="link" href="overload1.html#asio.reference.defer.overload1.return_value">Return
Value</a>
</h6>
<p>
This function returns <code class="computeroutput"><span class="identifier">async_initiate</span><span class="special">&lt;</span><span class="identifier">NullaryToken</span><span class="special">,</span> <span class="keyword">void</span><span class="special">()&gt;(</span><span class="identifier">Init</span><span class="special">{},</span> <span class="identifier">token</span><span class="special">)</span></code>,
where <code class="computeroutput"><span class="identifier">Init</span></code> is a function
object type defined as:
</p>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">Init</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">CompletionHandler</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">CompletionHandler</span><span class="special">&amp;&amp;</span> <span class="identifier">completion_handler</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="special">};</span>
</pre>
<p>
The function call operator of <code class="computeroutput"><span class="identifier">Init</span><span class="special">:</span></code>
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<p class="simpara">
Obtains the handler's associated executor object <code class="computeroutput"><span class="identifier">ex</span></code>
of type <code class="computeroutput"><span class="identifier">Ex</span></code> by performing
</p>
<pre class="programlisting"><span class="keyword">auto</span> <span class="identifier">ex</span> <span class="special">=</span> <span class="identifier">get_associated_executor</span><span class="special">(</span><span class="identifier">handler</span><span class="special">);</span>
</pre>
</li>
<li class="listitem">
<p class="simpara">
Obtains the handler's associated allocator object <code class="computeroutput"><span class="identifier">alloc</span></code>
by performing
</p>
<pre class="programlisting"><span class="keyword">auto</span> <span class="identifier">alloc</span> <span class="special">=</span> <span class="identifier">get_associated_allocator</span><span class="special">(</span><span class="identifier">handler</span><span class="special">);</span>
</pre>
</li>
<li class="listitem">
<p class="simpara">
If <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span class="identifier">is_executor</span><span class="special">&lt;</span><span class="identifier">Ex</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is true, performs
</p>
<pre class="programlisting"><span class="identifier">prefer</span><span class="special">(</span>
<span class="identifier">require</span><span class="special">(</span><span class="identifier">ex</span><span class="special">,</span> <span class="identifier">execution</span><span class="special">::</span><span class="identifier">blocking</span><span class="special">.</span><span class="identifier">never</span><span class="special">),</span>
<span class="identifier">execution</span><span class="special">::</span><span class="identifier">relationship</span><span class="special">.</span><span class="identifier">continuation</span><span class="special">,</span>
<span class="identifier">execution</span><span class="special">::</span><span class="identifier">allocator</span><span class="special">(</span><span class="identifier">alloc</span><span class="special">)</span>
<span class="special">).</span><span class="identifier">execute</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">CompletionHandler</span><span class="special">&gt;(</span><span class="identifier">completion_handler</span><span class="special">));</span>
</pre>
</li>
<li class="listitem">
<p class="simpara">
If <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span class="identifier">is_executor</span><span class="special">&lt;</span><span class="identifier">Ex</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is false, performs
</p>
<pre class="programlisting"><span class="identifier">ex</span><span class="special">.</span><span class="identifier">defer</span><span class="special">(</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">CompletionHandler</span><span class="special">&gt;(</span><span class="identifier">completion_handler</span><span class="special">),</span>
<span class="identifier">alloc</span><span class="special">);</span>
</pre>
</li>
</ul></div>
<h6>
<a name="asio.reference.defer.overload1.h2"></a>
<span><a name="asio.reference.defer.overload1.completion_signature"></a></span><a class="link" href="overload1.html#asio.reference.defer.overload1.completion_signature">Completion
Signature</a>
</h6>
<pre class="programlisting"><span class="keyword">void</span><span class="special">()</span>
</pre>
</div>
<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or 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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