Angular2反應形式下拉菜單

Question

我只是在學習angular 2，並且有一種情況，我正在創建一個將成為一件設備的表格。 與設備關聯的領域之一是建築物。 當用戶編輯或添加新設備時，我希望向他們顯示一個下拉列表，其中包含可以分配設備的建築物列表。 設備詳細信息組件如下：

  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)
  }
}

equipment-detail 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>

當我單擊下拉選項時，我得到一個代表所選建築物的對象。 結果是

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

當我單擊保存按鈕並查看與formcontrol關聯的數據時，建築物不再是對象，而只是buildingId。

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

如何獲得要與建築物對象一起設置的主要設備對象，而不僅僅是建築物ID？

Answer 1

這是因為您具有building.id value屬性，這就是為什么它在選擇選項時分配building.id的原因。 您應該考慮將整個building對象的value屬性綁定更改為ngValue 。

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