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What does Litho's @FromPrepare annotation do?

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?

Solution

  • 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