dynamic ngOnChanges(Map<String, SimpleChange> changes)

Source 

ngOnChanges(Map<String, SimpleChange> changes) {
  if (!this._added) {
    this.formDirective.addControl(this);
    this._added = true;
  }
  if (isPropertyUpdated(changes, this.viewModel)) {
    this.viewModel = this.model;
    this.formDirective.updateModel(this, this.model);
  }
}