Method addCallback

src/Deferred.java:720–722

Registers a callback. If the deferred result is already available and isn't an exception, the callback is executed immediately from this thread. If the deferred result is already available and is an exception, the callback is discarded. If the deferred result is not available, this callback is q

(final Callback<R, T> cb)

   * @return {@code this} with an "updated" type.
   */
  public <R> Deferred<R> addCallback(final Callback<R, T> cb) {
    return addCallbacks(cb, Callback.PASSTHROUGH);
  }

  /**
   * Registers a callback.