ter.future; // Send future object back to client.
  }

  // Something calls this when the value is ready.
  void _finishOperation(T result) {
    _completer.complete(result);
  }

  // If something goes wrong, call this.
  void _errorHappened(error) {
    _completer.completeError(error);
  }
}
</code></pre>
    </section>
    

    <section class="summary offset-anchor" id="constructors">
      <h2>Constructors</h2>

      <dl class="constructor-summary-list">
        <dt id="Completer" class="callable">
  