javascript - Angular2 react 形式下拉

Question

我刚刚学习 angular 2，并且有一个案例，我正在创建一个将成为一件设备的表单。与设备关联的字段之一是建筑物。当用户正在编辑或添加新设备时，我希望向他们显示一个下拉列表，其中包含他们可以将设备分配给的建筑物列表。 equipment-detail组件如下:

  export class EquipmentDetailComponent implements OnInit {
  equipment: IEquipment;
  equipmentForm: FormGroup;
  buildingList: Ibuilding[];

  constructor(private EquipmentService: EquipmentService,
              private BuildingsService: BuildingsService) { }

  ngOnInit() {
    this.equipment = this.EquipmentService.getEquipmentDetail(1);
    this.buildingList = this.BuildingsService.getBuildingList();

    let id = new FormControl(this.equipment.id);
    let unit = new FormControl(this.equipment.unit);
    let active = new FormControl(this.equipment.active);
    let building = new FormControl(this.equipment.building.id);

    this.equipmentForm = new FormGroup({
      id: id,
      unit: unit,
      active: active,
      building: building
    })    
  }

  saveEquipment(formValues){
    console.log(formValues);
  }

  onSelect(id){
    this.equipment.building = this.BuildingsService.getBuildingDetail(id);
    console.log(this.equipment.building)
  }
}

设备详情html如下:

<div class="col-md-2">
  <form [formGroup]="equipmentForm" (ngSubmit)="saveEquipment(equipmentForm.value)" autocomplete="off" novalidate>
    <div class="form-group">
      <label form="unit">Unit:</label>
      <input formControlName="unit" id="unit" type="text" class="form-control" placeholder="Unit...."/>
    </div>
    <div class="form-group">
      <label form="active">Active:</label>
      <input formControlName="active" id="active" type="checkbox" class="form-control"/>
    </div>
    <div class="form-group">
      <label form="building">Building:</label>
      <select class="form-control" formControlName="building" (change)="onSelect($event.target.value)">
        <option *ngFor="let building of buildingList" value={{building.id}}>
          {{building.buildingName}}
        </option>
      </select>
    </div>
    <button type="submit" class="btn btn-primary">Save</button>
  </form>
</div>

当我单击下拉选项时，我得到一个代表我选择的建筑物的对象。结果是

Object {id: 2, buildingName: "Building 2", active: true}
   active: true
   buildingName: "Building 2"
   id: 2

当我单击保存按钮并查看与 formcontrol 关联的数据时，建筑物不再是一个对象，它只是 buildingId。

Object {id: 1, unit: "Item 1", active: true, building: "2"}
   active: true
   building: "2"
   id: 1
   unit:"Item 1"
   __proto__: Object

如何让主要设备对象与建筑物对象一起设置，而不仅仅是建筑物 ID？

Answer 1

这是因为您具有 building.id 的 value 属性，这就是它在选项选择时分配 building.id 的原因。您应该考虑将整个 building 对象的 value 属性绑定(bind)更改为 ngValue。

<select class="form-control" formControlName="building" (change)="onSelect($event.target.value)">
  <option *ngFor="let building of buildingList" [ngValue]="building">
    {{building.buildingName}}
  </option>
</select>