eLibrary.Cancelable"></a>
      <a id="observeWithOldValue((Option[A],A)⇒Unit):Cancelable"></a>
      <h4 class="signature">
      <span class="modifier_kind">
        <span class="modifier"></span>
        <span class="kind">def</span>
      </span>
      <span class="symbol">
        <span class="name">observeWithOldValue</span><span class="params">(<span name="f">f: (<span class="extype" name="scala.Option">Option</span>[<span class="extype" name="react.core.ReactiveLibrary.SignalTrait.A">A</span>], <s