Class Continue

src/Deferred.java:1342–1376

A Callback to resume execution after another Deferred.

   * A {@link Callback} to resume execution after another Deferred.
   */
  private final class Continue implements Callback<Object, Object> {
    private final Deferred d;
    private final Callback cb;

    /**
     * Constructor.
     * @param d The other Deferred we need to resume after.
     * @param cb The callback that returned that Deferred or {@code null} if we
     * don't know where this Deferred comes from (it was our initial result).
     */
    public Continue(final Deferred d, final Callback cb) {
      this.d = d;
      this.cb = cb;
    }

    public Object call(final Object arg) {
      if (arg instanceof Deferred) {
        handleContinuation((Deferred) arg, cb);
      } else if (!casState(PAUSED, RUNNING)) {
        final String cb2s = cb == null ? "null" : cb + "@" + cb.hashCode();
        throw new AssertionError("Tried to resume the execution of "
          + Deferred.this + ") although it's not in state=PAUSED."
          + "  This occurred after the completion of " + d
          + " which was originally returned by callback=" + cb2s);
      }
      result = arg;
      runCallbacks();
      return arg;
    }

    public String toString() {
      return "(continuation of Deferred@" + Deferred.super.hashCode()
        + " after " + (cb != null ? cb + "@" + cb.hashCode() : d) + ')';
    }
  };

  /**
   * Returns a helpful string representation of this {@code Deferred}.