Runtime Considerations for Flow Screen Components

When you’re configuring components for flows, review these considerations for defining attributes and flow runtime behavior.

  • Handle null default input values.

    If a flow admin doesn't set a default input value for a custom screen component, Flow Builder passes a null value at component run time. To set a default value at run time, add a null handler.

  • Handle hidden component output values.

    If a screen component is hidden, all output attributes are set to null when the user navigates away from the screen.

  • Notify runtime of attribute changes.

    Lightning web components use events to report changes from components to flows. To notify the flow runtime of attribute changes, a component fires the FlowAttributeChangeEvent event. For example, use this event when using conditional visibility to render a screen component when conditions are met or when mapping the value of output attributes to flow variables. For code samples, see lightning-flow-support.

  • Consider the default attribute behavior.

    All flow screen component input attributes are also output attributes by default.

See Also