Angular4：选择[选定]第一次无效

Question

有一个代码：

<select name="department" class="form-control select" [(ngModel)]="departments" formControlName="departmentControl">    
    <option *ngFor="let department of departments" [ngValue]="department" [selected]="department.id == this.departmentid">
      {{ department.name }}
    </option>
  </select>

和功能：

isSelected(department): boolean {
  debugger;
  return department.id == this.departmentid;
}

部门-是用户详细信息组件的嵌套组件。首次选择用户详细信息组件后，未选择部门。但是第二次一切正常。哪里有错？

Answer 1

无需：[selected]="department.id == this.departmentid"正在使用时[(ngModel)]

更改[(ngModel)]="departments"为[(ngModel)]="departmentid"

更改[ngValue]="department"为[ngValue]="department.id"

最后，它应该看起来像这样：

<select name="department" class="form-control select" [(ngModel)]="departmentid" formControlName="departmentControl">    
    <option *ngFor="let department of departments" [ngValue]="department.id" >
        {{ department.name }}
    </option>
</select>

工作演示