Angular2单选按钮验证

Question

我尝试过但不起作用如何在angular 2中验证单选按钮以及复选框和邮政编码。任何人都可以找到解决方案。请帮助我解决此问题。 演示：https://stackblitz.com/edit/angular-7-template-driven-form-validation-ndspdl?file=app/app.component.html

    <div class="form-group">
    Radio Buttons:
    <div *ngFor="let enum of enum_details">
    <label for="enum_answer_{{enum.name}}">
    <input id="enum_answer_{{enum.name}}" [value]='enum.name' type="radio" 
    name="enums" enums="ngModel" [(ngModel)]="radioSelected">
    {{enum.name}}
    </label>
    </div>  
    </div>  

    <div class="form-group">
    Checkboxes:
    <div *ngFor="let item of items; let i = index" class="checkbox"> 
        <label for="{{item.id}}">
            <input type="checkbox" value="{{item.id}}" required id=" 
    {{item.id}}" #chk="ngModel" [(ngModel)]="item.isSelected" 
   name="name+str(i)" (change)="CheckBoxChanged(i,$event)" />
            <span class="text-body">{{item.name}}</span>
        </label>
    </div>
    </div>