Angular2 反应式表单 - 使用下拉菜单设置表单字段的默认值

html
<select [(ngModel)]="selectedValue">
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

typescript
export class MyComponent {
  selectedValue: string;
  constructor() {
    this.selectedValue = "option2";
  }
}

typescript
export class MyComponent implements OnChanges {
  @Input() isLoggedIn: boolean;
  selectedValue: string;
  ngOnChanges() {
    if (this.isLoggedIn) {
      this.selectedValue = "option1";
    } else {
      this.selectedValue = "option2";
    }
  }
}

html
<select [(ngModel)]="selectedValue">
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

typescript
export class MyComponent {
  selectedValue: string;
  constructor() {
    this.selectedValue = "option2";
  }
}

typescript
export class MyComponent implements OnChanges {
  @Input() isLoggedIn: boolean;
  selectedValue: string;
  ngOnChanges() {
    if (this.isLoggedIn) {
      this.selectedValue = "option1";
    } else {
      this.selectedValue = "option2";
    }
  }
}