Function twoWayBinding

packages/core/src/render3/dynamic_bindings.ts:219–245

(publicName: string, value: WritableSignal<unknown>)

 * @see [Binding inputs, outputs and setting host directives at creation](guide/components/programmatic-rendering#binding-inputs-outputs-and-setting-host-directives-at-creation)
 */
export function twoWayBinding(publicName: string, value: WritableSignal<unknown>): Binding {
  const input = inputBinding(publicName, value) as BindingInternal;
  const output = outputBinding(publicName + 'Change', (eventValue) =>
    value.set(eventValue),
  ) as BindingInternal;

  // We take advantage of inputs only having a `create` block and outputs only having an `update`
  // block by passing them through directly instead of creating dedicated functions here. This
  // assumption can break down if one of them starts targeting both blocks. These assertions
  // are here to help us catch it if something changes in the future.
  ngDevMode && assertNotDefined(input.create, 'Unexpected `create` callback in inputBinding');
  ngDevMode && assertNotDefined(output.update, 'Unexpected `update` callback in outputBinding');

  const binding: BindingInternal = {
    [BINDING]: {
      kind: 'twoWay',
      requiredVars: input[BINDING].requiredVars + output[BINDING].requiredVars,
    },
    set targetIdx(idx: number) {
      (input as Writable<BindingInternal>).targetIdx = idx;
      (output as Writable<BindingInternal>).targetIdx = idx;
    },
    create: output.create,
    update: input.update,
  };
  return binding;
}