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template&lt;template&lt; typename U, typename V, typename...Args &gt; class ObjectType = std::map, template&lt; typename U, typename...Args &gt; class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = int64_t, class NumberFloatType = double, template&lt; typename U &gt; class AllocatorType = std::allocator&gt; </div>
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<td class="memname">void <a class="el" href="classnlohmann_1_1basic__json.html">nlohmann::basic_json</a>::clear </td>
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<td class="paramname"></td><td>)</td>
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<span class="mlabels"><span class="mlabel">inline</span><span class="mlabel">noexcept</span></span> </td>
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<p>Clears the content of a JSON value and resets it to the default value as if <a class="el" href="classnlohmann_1_1basic__json_a793e5c1da2fc7de7a04b19eadbb3f2cb.html#a793e5c1da2fc7de7a04b19eadbb3f2cb">basic_json(value_t)</a> would have been called:</p>
<table class="doxtable">
<tr>
<th>Value type </th><th>initial value </th></tr>
<tr>
<td>null </td><td><code>null</code> </td></tr>
<tr>
<td>boolean </td><td><code>false</code> </td></tr>
<tr>
<td>string </td><td><code>""</code> </td></tr>
<tr>
<td>number </td><td><code>0</code> </td></tr>
<tr>
<td>object </td><td><code>{}</code> </td></tr>
<tr>
<td>array </td><td><code>[]</code> </td></tr>
</table>
<dl class="section note"><dt>Note</dt><dd>Floating-point numbers are set to <code>0.0</code> which will be serialized to <code>0</code>. The vale type remains <a class="el" href="classnlohmann_1_1basic__json_aacf6c869f6a9c66ac1bc99e93f310044.html#aacf6c869f6a9c66ac1bc99e93f310044">number_float_t</a>.</dd></dl>
<dl class="section user"><dt>Complexity</dt><dd>Linear in the size of the JSON value.</dd></dl>
<dl class="section user"><dt>Example</dt><dd>The example below shows the effect of <a class="el" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a> to different JSON value types. <div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;<span class="preprocessor">#include &lt;json.hpp&gt;</span></div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;<span class="keyword">using namespace </span><a class="code" href="namespacenlohmann.html">nlohmann</a>;</div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160;</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160;<span class="keywordtype">int</span> main()</div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;{</div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160; <span class="comment">// create JSON values</span></div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_null;</div>
<div class="line"><a name="l00009"></a><span class="lineno"> 9</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_boolean = <span class="keyword">true</span>;</div>
<div class="line"><a name="l00010"></a><span class="lineno"> 10</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_number_integer = 17;</div>
<div class="line"><a name="l00011"></a><span class="lineno"> 11</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_number_float = 23.42;</div>
<div class="line"><a name="l00012"></a><span class="lineno"> 12</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_object = {{<span class="stringliteral">&quot;one&quot;</span>, 1}, {<span class="stringliteral">&quot;two&quot;</span>, 2}};</div>
<div class="line"><a name="l00013"></a><span class="lineno"> 13</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_array = {1, 2, 4, 8, 16};</div>
<div class="line"><a name="l00014"></a><span class="lineno"> 14</span>&#160; <a class="code" href="classnlohmann_1_1basic__json.html">json</a> j_string = <span class="stringliteral">&quot;Hello, world&quot;</span>;</div>
<div class="line"><a name="l00015"></a><span class="lineno"> 15</span>&#160;</div>
<div class="line"><a name="l00016"></a><span class="lineno"> 16</span>&#160; <span class="comment">// call clear()</span></div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span>&#160; j_null.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span>&#160; j_boolean.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span>&#160; j_number_integer.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span>&#160; j_number_float.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span>&#160; j_object.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span>&#160; j_array.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span>&#160; j_string.<a class="code" href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">clear</a>();</div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span>&#160;</div>
<div class="line"><a name="l00025"></a><span class="lineno"> 25</span>&#160; <span class="comment">// serialize the cleared values()</span></div>
<div class="line"><a name="l00026"></a><span class="lineno"> 26</span>&#160; std::cout &lt;&lt; j_null &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00027"></a><span class="lineno"> 27</span>&#160; std::cout &lt;&lt; j_boolean &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>&#160; std::cout &lt;&lt; j_number_integer &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00029"></a><span class="lineno"> 29</span>&#160; std::cout &lt;&lt; j_number_float &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00030"></a><span class="lineno"> 30</span>&#160; std::cout &lt;&lt; j_object &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>&#160; std::cout &lt;&lt; j_array &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span>&#160; std::cout &lt;&lt; j_string &lt;&lt; <span class="charliteral">&#39;\n&#39;</span>;</div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span>&#160;}</div>
<div class="ttc" id="classnlohmann_1_1basic__json_html"><div class="ttname"><a href="classnlohmann_1_1basic__json.html">nlohmann::basic_json</a></div><div class="ttdoc">a class to store JSON values </div><div class="ttdef"><b>Definition:</b> json.hpp:121</div></div>
<div class="ttc" id="namespacenlohmann_html"><div class="ttname"><a href="namespacenlohmann.html">nlohmann</a></div><div class="ttdoc">namespace for Niels Lohmann </div><div class="ttdef"><b>Definition:</b> json.hpp:56</div></div>
<div class="ttc" id="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a_html_a8c40cd9ead4de7c82f28268bdf0ec98a"><div class="ttname"><a href="classnlohmann_1_1basic__json_a8c40cd9ead4de7c82f28268bdf0ec98a.html#a8c40cd9ead4de7c82f28268bdf0ec98a">nlohmann::basic_json::clear</a></div><div class="ttdeci">void clear() noexcept</div><div class="ttdoc">clears the contents </div><div class="ttdef"><b>Definition:</b> json.hpp:2620</div></div>
</div><!-- fragment --> Output: <pre class="fragment">null
false
0
0
{}
[]
""
</pre> The example code above can be translated with<pre class="fragment">g++ -std=c++11 -Isrc doc/examples/clear.cpp -o clear </pre>. </dd></dl>
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