HarmonyOS使用@ObjectLink 数据不刷新 ？

Question

一个接口返回的Json转换后的集合，在@Component export struct UserDeviceItem { @ObjectLink item: DeviceModel } item的数据变化，页面没有刷新，是必须要new的才行？如何解决json转换使用的问题？

Answer 1

花花，你可以通过JSON.parse得到的对象并不是通过类构造出的实例，其数据变化无法被观测到，所以不能实现ui刷新可以通过引入三方库 reflect-metadata 和 class-transformer，参考如下demo实现：

// test.ts : 
export let jsonString:Record<string, ESObject> = { 
  "data" : [ 
    { 
      "number" :1, 
      "age": 20, 
      "testA": { 
        "str" : "123" 
      } 
    }, 
    { 
      "number" :2, 
      "age": 21, 
      "testA": { 
        "str" : "456" 
      } 
    } 
  ] 
} 
 
// Index.ets 
import { Type, plainToClass } from 'class-transformer' 
import 'reflect-metadata' 
import { jsonString } from './test' 
import { TestA, Person, ViewA} from './ViewA'; 
 
class ResponseObj { 
  @Type (() => Person) 
  data: Person[] = []; 
} 
@Entry 
@Component 
struct Index { 
  @State list: Person[] = []; 
  @State message: string = 'Click me'; 
  build() { 
    Row() { 
      Column() { 
        Text(this.message).fontSize(40).onClick(() => { 
          let responseObj : ResponseObj = plainToClass(ResponseObj, jsonString); 
          console.log(` ${responseObj.data[0] instanceof Person}`) 
          this.list = this.list.concat(responseObj.data); 
        }) 
 
        ForEach(this.list, (item : Person, index: number) => { 
          ViewA({index:index, testA: item.testA}) 
        }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
} 
 
// ViewA.ets 
import { Type } from 'class-transformer' 
@Observed 
export class TestA { 
  public str : string 
 
  constructor(str: string) { 
    this.str = str; 
  } 
} 
export class Person { 
  name: string = '' 
  age: number = 1 
 
  @Type(()=>TestA) 
  testA: TestA = new TestA('') 
} 
@Component 
export struct ViewA { 
  @ObjectLink testA: TestA 
  index: number = -1; 
  build() { 
    Row(){ 
      Button(`View A ${this.testA.str}`).onClick(() =>{ 
        this.index += 1; 
        this.testA.str = `${this.index} : Test A String` 
      }) 
    }.margin({top : 10 }) 
  } 
}