angular/angular · error · Error

@Output ${propertyName} not initialized in '${instance.const

Error message

@Output ${propertyName} not initialized in '${instance.constructor.name}'.

What it means

Error "@Output ${propertyName} not initialized in '${instance.constructor.name}'." thrown in angular/angular.

Source

Thrown at packages/core/src/render3/view/directive_outputs.ts:122

}

export function listenToOutput(
  tNode: TNode,
  lView: LView,
  directiveIndex: number,
  lookupName: string,
  eventName: string,
  listenerFn: WrappedEventCallback,
) {
  ngDevMode && assertIndexInRange(lView, directiveIndex);
  const instance = lView[directiveIndex];
  const tView = lView[TVIEW];
  const def = tView.data[directiveIndex] as DirectiveDef<unknown>;
  const propertyName = def.outputs[lookupName];
  const output = instance[propertyName];

  if (ngDevMode && !isOutputSubscribable(output)) {
    throw new Error(`@Output ${propertyName} not initialized in '${instance.constructor.name}'.`);
  }

  const subscription = (output as SubscribableOutput<unknown>).subscribe(listenerFn);
  storeListenerCleanup(tNode.index, tView, lView, eventName, listenerFn, subscription, true);
}

/**
 * Whether the given value represents a subscribable output.
 *
 * For example, an `EventEmitter, a `Subject`, an `Observable` or an
 * `OutputEmitter`.
 */
function isOutputSubscribable(value: unknown): value is SubscribableOutput<unknown> {
  return (
    value != null && typeof (value as Partial<SubscribableOutput<unknown>>).subscribe === 'function'
  );
}

View on GitHub (pinned to 51cb07e980)

Solutions

1. Initialize the @Output with an EventEmitter or output() in the directive class.

When it happens

Trigger: Thrown at packages/core/src/render3/view/directive_outputs.ts:122 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of angular/angular@51cb07e980 (2026-08-22). Data as JSON: /api/errors/36a77b239ee581c8. Report an issue: GitHub.