HarmonyOS使用as关键字转换为指定类型，结果为undefined

import { ValueType } from '@kit.ArkData'; 
@Entry 
@Component 
struct AsDemo { 
  @State message: string = 'Hello World'; 
  aboutToAppear(): void { 
    let params: RouterParams = new RouterParams() 
    let stockParams = params as StockChartPageModel 
    params.param = {"name":"tom"} 
    console.log('父类集合内容：'+stockParams.param["name"]) 
  } 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
} 
export class RouterParams{ 
  param : Record<string,object | ValueType> = {} 
} 
export class StockChartPageModel extends RouterParams{ 
  stockCodes: Array<string> = [] 
}