Hongmeng Next State Management V2 – خلاصه استفاده از @Once Initialization

@ComponentV2
struct CompA {
  @Param @Once onceParam: string = "onceParam"; // 正确用法
  @Once onceStr: string = "Once"; // 错误用法，@Once无法单独使用
  @Local @Once onceLocal: string = "onceLocal"; // 错误用法，@Once不能与@Local一起使用
}
@Component
struct Index {
  @Once @Param onceParam: string = "onceParam"; // 错误用法
}

@ComponentV2
struct CompA {
  @Param @Once param1: number;
  @Once @Param param2: number;
}

@ComponentV2
struct CompA {
  @Param @Once onceParam: string = '';
  build() {
      Column() {
        Text(`onceParam: ${this.onceParam}`)
      }
  }
}

@Entry
@ComponentV2
struct CompB {
  @Local message: string = "Hello World";
  build() {
      Column() {
      Text(`Parent message: ${this.message}`)
      Button("change message")
       .onClick(() => {
          this.message = "Hello Tomorrow";
        })
      CompA({ onceParam: this.message })
      }
  }
}

@ObservedV2
class Info {
  @Trace name: string;
  constructor(name: string ) {
    this.name = name;
  }
}

@ComponentV2
struct Child {
  @Param @Once onceParamNum: number = 0;
  @Param @Once @Require onceParamInfo: Info;
  build() {
    Column() {
      Text(`Child onceParamNum: ${this.onceParamNum}`)
      Text(`Child onceParamInfo: ${this.onceParamInfo.name}`)
      Button("changeOnceParamNum")
       .onClick(() => {
          this.onceParamNum++;
        })
      Button("changeParamInfo")
       .onClick(() => {
          this.onceParamInfo = new Info("Cindy");
        })
    }
  }
}

@Entry
@ComponentV2
struct Index {
  @Local localNum: number = 10;
  @Local localInfo: Info = new Info("Tom");
  build() {
    Column() {
      Text(`Parent localNum: ${this.localNum}`)
      Text(`Parent localInfo: ${this.localInfo.name}`)
      Button("changeLocalNum")
       .onClick(() => {
          this.localNum++;
        })
      Button("changeLocalInfo")
       .onClick(() => {
          this.localInfo = new Info("Cindy");
        })
      Child({
        onceParamNum: this.localNum,
        onceParamInfo: this.localInfo
      })
    }
  }
}