e>ifAbsent</code>
and adds the key with the returned value to the map.</p>
<p>It's an error if the key is not present and <code>ifAbsent</code> is not provided.</p>
    </section>
    
    <section class="summary source-code" id="source">
      <h2><span>Implementation</span></h2>
      <pre class="language-dart"><code class="language-dart">V update(K key, V update(V value), {V Function()? ifAbsent}) =&gt;
    _map.update(key, update, ifAbsent: ifAbsent);</code></pre>
    </section>

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