Multiselect angular with form validation

controller.ts

public isMultiSelectOptionSelected(object: any): boolean {
    return object && Object.keys(object).some(key => object[key]);
}

view.html

<label ng-repeat="option in question.options">
    <input ng-required="!vm.isMultiSelectOptionSelected(question.selectedAnswer)" type="checkbox" ng-model="question.selectedAnswer[option]" name="{{question.id}}" />
    <span class="input custom-check"></span>
    <span class="question-label">{{option}}</span>
</label>