Html 为什么类型错误：无法读取属性'；无效'；未定义的角度（角度4）

我正在创建我的第一个角度项目。我想验证我的表单。 html:

为什么我要在浏览器控制台中排队

此错误：

ERROR TypeError: Cannot read property 'invalid' of undefined
at Object.eval [as updateDirectives] (RoomInformationCardComponent.html:92)
at Object.debugUpdateDirectives [as updateDirectives] (core.es5.js:13067)
at checkAndUpdateView (core.es5.js:12251)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)

请解释我为什么会遇到这个错误？是否与尚未创建的表单相关

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如何解决此问题？

首先生成模板，然后将模板引用绑定到组件变量。首先需要确保模板引用已绑定，然后才能使用它

---

您可以将运算符（？）与它们一起使用

countOfChildBedInput？。无效

在声明时将其赋值为false。

export class RoomInformationCardComponent implements OnInit {
  existChildBedInRoom: boolean;
  @ViewChild('childBedInRoom') childBedInRoom: ElementRef;

  constructor() { }

  ngOnInit() {
    this.existChildBedInRoom = false;
  }

}

ERROR TypeError: Cannot read property 'invalid' of undefined
at Object.eval [as updateDirectives] (RoomInformationCardComponent.html:92)
at Object.debugUpdateDirectives [as updateDirectives] (core.es5.js:13067)
at checkAndUpdateView (core.es5.js:12251)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)
at execComponentViewsAction (core.es5.js:12531)
at checkAndUpdateView (core.es5.js:12257)
at callViewAction (core.es5.js:12599)