) -&gt; </span><span class='decorator'>Result</span></code>
                </a>
              
              
              <div class="abstract">
                <div class="content">Atomically mutate this subject’s value in a closure where you can read and write the current element value</div>
              </div>
            </div>
          
            <div class="link-block topic">
              
                <a href="../../../documentation/swiftrex/replaylastsubjecttype/mutate(when:action:).htm