What does Litho's @FromPrepare annotation do?

Question

I have been reading Litho's documentation and I found this code example

@LayoutSpec(events = { ColorChangedEvent.class })
class ColorComponentSpec {
  ...
  @OnCreateLayout
  static ComponentLayout onCreateLayout(
      Context c,
      @Prop EventHandler colorChangedHandler,
      @FromPrepare int color) {
    ...
    ColorComponent.dispatchColorChangedEvent(
        colorChangedHandler,
        color);
    ...
  }
}

What does the @FromPrepare annotation do?

Answer 1

EDIT: this is an error in the docs. @FromPrepare should only be used in MountSpecs, not in LayoutSpecs.

@FromPrepare gives you an output that was returned from the OnPrepare method. You can read more about this pattern here: http://fblitho.com/docs/mount-specs#inter-stage-inputs-and-outputs