Trying to setValidations to a child component

and this below doesn’t seem to work?! Can anyone help?
control is my FormControl @Input()

ngOnInit() {
    const { structureDefinitionUrl, structureDefinitionId } = this.element;
    this.options =
      structureDefinitionUrl && structureDefinitionId
        ? this.getOptionsFromStructureDefinition(
            structureDefinitionUrl,
            structureDefinitionId
          )
        : [];
      this.control.setValidators([
        Validators.required,
        Validators.minLength(1)
      ]);
  }