Angular 5 - 使用模板驱动表单的动态表单验证

Question

我正在动态创建表单字段，ngFor并且每个字段都有唯一的name属性。我正在努力验证他们。我的示例代码：

<div *ngFor="let dimension of lstShippingDimensions; let i = index" class="dimension-item">
        <input type="text" name="units-{{i}}" [(ngModel)]="dimension.units" 
        class="first-f" placeholder="# of units" required>
        <input type="text" name="width-{{i}}" [(ngModel)]="dimension.width" 
        class="second-f" placeholder="W" required>
        <input type="text" name="height-{{i}}" [(ngModel)]="dimension.height" 
        class="third-f" placeholder="H" required>
        <input type="text" name="length-{{i}}" [(ngModel)]="dimension.length" 
        class="forth-f" placeholder="L" required>
        <select class="five-f" name="unitType-{{i}}" [(ngModel)]="dimension.unitType" 
        required>
            <option>inches</option>
            <option>feet</option>
        </select>
        <div *ngIf="!units-{{i}}.valid && units-{{i}}.touched" class="text-danger text-left">
            <small *ngIf="units-{{i}}.errors.required">Field is required.</small>
        </div>
    </div>

Answer 1

以某种方式解决了这个问题，只需添加#units="ngModel". 我猜 Angular 正在处理引用ngFor本身。这工作得很好：

<div *ngFor="let dimension of lstShippingDimensions; let i = index" class="dimension-item">
    <input type="text" name="units-{{i}}" #units="ngModel" [(ngModel)]="dimension.units" class="first-f" placeholder="# of units" required>
    <input type="text" name="width-{{i}}" [(ngModel)]="dimension.width" class="second-f" placeholder="W" required>
    <input type="text" name="height-{{i}}" [(ngModel)]="dimension.height" class="third-f" placeholder="H" required>
    <input type="text" name="length-{{i}}" [(ngModel)]="dimension.length" class="forth-f" placeholder="L" required>
    <select class="five-f" name="unitType-{{i}}" [(ngModel)]="dimension.unitType" required>
        <option>inches</option>
        <option>feet</option>
    </select>
    <div *ngIf="!units.valid && units.touched" class="text-danger text-left">
        <small># of units is required.</small>
    </div>
</div>