HarmonyOS 如何在父组件中调用子组件的方法

@Component
struct Child  {
  @State private text: string = '初始值'
  private controller: ChildController = new ChildController();

  aboutToAppear() {
    if(this.controller) {
      //给controller对应的方法赋值
      this.controller.changeText = this.changeText
    }
  }

  //封装的能力
  private changeText = (value: string) =>{
    this.text = value
  }

  build() {
    Column() {
      Text(this.text)
    }
  }
}

//定义controller对象
class ChildController {
  changeText = (value: string) => {}
}

@Entry
@Component
struct Parent {
  private  ChildRef = new ChildController()
  build() {
    Column() {
      Text('调用Child的changeText').fontSize('18vp').fontColor(Color.Gray)
      Divider()
      Child({ controller:this. ChildRef })
      Button('Parent调用childer的changeText').onClick(() => {
        this.ChildRef.changeText('Parent调用childer的changeText')
      })
    }
    .justifyContent(FlexAlign.Center)
    .width("100%")
    .height("100%")
  }
}