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<div class="title">Default Arguments </div> </div>
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<div class="textblock"><p>When you want to register a <a class="el" href="classrttr_1_1method.html">method</a> or a <a class="el" href="classrttr_1_1constructor.html">constructor</a> which contains default arguments, you have to provide them RTTR explicitly. The reason for this is, default arguments are not part of the function signature. Nevertheless, RTTR provides a mechanism to register functions with default arguments.</p>
<p>Please take a look at following example:</p>
<div class="fragment"><div class="line"><span class="keyword">using namespace </span><a class="code" href="namespacerttr.html">rttr</a>;</div><div class="line"></div><div class="line"><span class="keywordtype">void</span> my_function(<span class="keywordtype">int</span> a, <span class="keywordtype">bool</span> b, <span class="keyword">const</span> std::string& text, <span class="keyword">const</span> <span class="keywordtype">int</span>* ptr);</div><div class="line"></div><div class="line"><a class="code" href="registration_8h.html#ac6326400f16225ee15b52eabcaae8130">RTTR_REGISTRATION</a></div><div class="line">{</div><div class="line"> <a class="code" href="classrttr_1_1registration.html#a5da1c6eb947d700681faa7fec0bf23b7">registration::method</a>(<span class="stringliteral">"my_function"</span>, &my_function) </div><div class="line"> (</div><div class="line"> <a class="code" href="namespacerttr.html#afdaed4515c436b34b8e24af714a09c64">default_arguments</a>(<span class="keyword">true</span>, std::string(<span class="stringliteral">"default text"</span>), <span class="keyword">nullptr</span>)</div><div class="line"> );</div><div class="line">}</div></div><!-- fragment --><p>The default arguments has to be provided via the function: <a class="el" href="namespacerttr.html#afdaed4515c436b34b8e24af714a09c64">default_arguments()</a>. Place the call in the <code>()</code> operator of the returned <a class="el" href="classrttr_1_1registration_1_1bind.html">bind</a> object.</p>
<p>The function has following synopsis: </p><div class="fragment"><div class="line"><span class="keyword">template</span><<span class="keyword">typename</span>...TArgs></div><div class="line">detail::default_args<TArgs...> <a class="code" href="namespacerttr.html#afdaed4515c436b34b8e24af714a09c64">default_arguments</a>(TArgs&&...args)</div></div><!-- fragment --><p> The values will be copied internally and will be provided during invoke of the method or constructor, when the corresponding argument is missing:</p>
<div class="fragment"><div class="line"><span class="keywordtype">int</span> main()</div><div class="line">{</div><div class="line"> <span class="keyword">using namespace </span><a class="code" href="namespacerttr.html">rttr</a>;</div><div class="line"> <a class="code" href="classrttr_1_1method.html">method</a> meth = <a class="code" href="classrttr_1_1type.html#a15fa4ae4fb0619be68c3b83967fefb51">type::get_global_method</a>(<span class="stringliteral">"my_function"</span>);</div><div class="line"> <span class="comment">// the default values: 'true', 'std::string("default text"'), 'nullptr' will be forwarded by RTTR automatically</span></div><div class="line"> <a class="code" href="classrttr_1_1variant.html">variant</a> var = meth.<a class="code" href="classrttr_1_1method.html#aea4351075b4cbe6f2f2b6500cf226f20">invoke</a>(<a class="code" href="classrttr_1_1instance.html">instance</a>(), 23);</div><div class="line"> std::cout << var.<a class="code" href="classrttr_1_1variant.html#aed6e6a2e29b4d1ac51a09b7d9037dd44">is_valid</a>(); <span class="comment">// prints 'true'</span></div><div class="line"></div><div class="line"> <span class="comment">// the default value: 'nullptr' will be forwarded by RTTR automatically</span></div><div class="line"> var = meth.<a class="code" href="classrttr_1_1method.html#aea4351075b4cbe6f2f2b6500cf226f20">invoke</a>(<a class="code" href="classrttr_1_1instance.html">instance</a>(), 23, <span class="keyword">true</span>, std::string(<span class="stringliteral">"text"</span>));</div><div class="line"> std::cout << var.<a class="code" href="classrttr_1_1variant.html#aed6e6a2e29b4d1ac51a09b7d9037dd44">is_valid</a>(); <span class="comment">// prints 'true'</span></div><div class="line">}</div></div><!-- fragment --><dl class="section remark"><dt>Remarks</dt><dd>The given arguments must match the signature from the starting position to the right most argument.</dd></dl>
<p>The following snippet will <b>not</b> compile and will raise a <em>static_assert</em>: </p><div class="fragment"><div class="line"><span class="keyword">using namespace </span><a class="code" href="namespacerttr.html">rttr</a>;</div><div class="line"></div><div class="line"><span class="keywordtype">void</span> my_function(<span class="keywordtype">int</span> a, <span class="keywordtype">bool</span> b, <span class="keyword">const</span> std::string& text, <span class="keyword">const</span> <span class="keywordtype">int</span>* ptr);</div><div class="line"></div><div class="line"><a class="code" href="registration_8h.html#ac6326400f16225ee15b52eabcaae8130">RTTR_REGISTRATION</a></div><div class="line">{</div><div class="line"> <a class="code" href="classrttr_1_1registration.html#a5da1c6eb947d700681faa7fec0bf23b7">registration::method</a>(<span class="stringliteral">"my_function"</span>, &my_function) </div><div class="line"> (</div><div class="line"> <a class="code" href="namespacerttr.html#afdaed4515c436b34b8e24af714a09c64">default_arguments</a>(std::string(<span class="stringliteral">"default text"</span>)) <span class="comment">// default value for "ptr" not given</span></div><div class="line"> );</div><div class="line">}</div></div><!-- fragment --><p>Every <a class="el" href="classrttr_1_1method.html">method</a> and <a class="el" href="classrttr_1_1constructor.html">constructor</a> can have default arguments.</p>
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