How to define parameters in Angular components?

I’ve a component modal which has a darkUnderneath property. I’m trying to bind it using [darkUnderneath]="true" in my parent component’s template and am getting:

Can’t bind to ‘darkUnderneath’ since it isn’t a known property of ‘modal’.

Do I need to use the @Output decorator? I tried defining darkUnderneath with and without the @Output decorator from @angular/core.

<modal [darkUnderneath]="blah"></modal>

export class ModalComponent implements OnInit {
  @Output()
  darkUnderneath: boolean = false;
  // ...
}

>Solution :

You’re looking for the @Input decorator.

export class ModalComponent implements OnInit {
  @Input()
  darkUnderneath: boolean = false;
  // ...
}