doWhile method - Future class - dart:async library

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The only restriction is a new call to <code>action</code> won't happen before the previous call has returned, and if it returned a <code>Future<bool></code>, not until that future has completed.</p> <p>Example:</p> <pre class="language-dart"><code class="language-dart">void main() async { var value = 0; await Future.doWhile(() async { value++; await Future.delayed(const Duration(seconds: 1)); if (value == 3) { print('Finished with $value'); return false; } return true; }); } // Outputs: 'Finished with 3' </code></pre> </section> <section class="summary source-code" id="source"> <h2><span>Implementation</span></h2> <pre class="language-dart"><code class="language-dart">static Future<void> doWhile(FutureOr<bool> action()) { _Future<void> doneSignal = new _Future<void>(); late void Function(bool) nextIteration; // Bind this callback explicitly so that each iteration isn't bound in the // context of all the previous iterations' callbacks. // This avoids, e.g., deeply nested stack traces from the stack trace // package. nextIteration = Zone.current.bindUnaryCallbackGuarded((bool keepGoing) { while (keepGoing) { FutureOr<bool> result; try { result = action(); } catch (error, stackTrace) { // Cannot use _completeWithErrorCallback because it completes // the future synchronously. _asyncCompleteWithErrorCallback(doneSignal, error, stackTrace); return; } if (result is Future<bool>) { result.then(nextIteration, onError: doneSignal._completeError); return; } keepGoing = result; } doneSignal._complete(null); }); nextIteration(true); return doneSignal; }</code></pre> </section> </div>  <div id="dartdoc-sidebar-left" class="sidebar sidebar-offcanvas-left">  <header id="header-search-sidebar" class="hidden-l"> <form class="search-sidebar" role="search"> <input type="text" id="search-sidebar" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search..."> </form> </header> <ol class="breadcrumbs gt-separated dark hidden-l" id="sidebar-nav"> <li><a href="../../index.html">Dart</a></li> <li><a href="../../dart-async/dart-async-library.html">dart:async</a></li> <li><a href="../../dart-async/Future-class.html">Future<span class="signature"><<wbr><span class="type-parameter">T</span>></span></a></li> <li class="self-crumb">doWhile static method</li> </ol> <h5>Future class</h5> <div id="dartdoc-sidebar-left-content"></div> </div> <div id="dartdoc-sidebar-right" class="sidebar sidebar-offcanvas-right"> </div> </main> <footer> <span class="no-break"> Dart 3.5.4 </span> <span class="glue-footer"> <span class="no-break"> | <a href="https://dart.dev/terms" title="Terms of use">Terms</a> </span> <span class="no-break"> | <a href="https://policies.google.com/privacy" target="_blank" rel="noopener" title="Privacy policy" class="no-automatic-external">Privacy</a> </span> <span class="no-break"> | <a href="https://dart.dev/security" title="Security philosophy and practices">Security</a> </span> <div class="copyright" style="font-size: 0.9em; color: darkgrey; margin-top: 0.5em;"> Except as otherwise noted, this site is licensed under a <a style="color: darkgrey;" href="https://creativecommons.org/licenses/by/4.0/"> Creative Commons Attribution 4.0 International License</a> and code samples are licensed under the <a style="color: darkgrey;" href="https://opensource.org/licenses/BSD-3-Clause" class="no-automatic-external"> 3-Clause BSD License</a> </div> </span> </footer> <script src="../../static-assets/highlight.pack.js?v1"></script> <script src="../../static-assets/docs.dart.js"></script> <button aria-hidden="true" class="glue-footer__link glue-cookie-notification-bar-control"> Cookies management controls </button> <script src="https://www.gstatic.com/glue/cookienotificationbar/cookienotificationbar.min.js" data-glue-cookie-notification-bar-category="2B"> </script> </body> </html>

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doWhile method - Future class - dart:async library - Dart API