HarmonyOS 开发有没有像vue里面计算属性的api，如果没有那如何实现呢

使用@watch注解监听变量。可以尝试如下demo

@Entry
@Component
struct Index {
  @State sum: number = 0;
  @Watch('numberChange') @State num1: number = 0;
  @Watch('numberChange') @State num2: number = 0;

  numberChange() {
    this.sum = this.num1 + this.num2
  }
  build() {
    Row() {
      Column() {
        Text("sum:" + this.sum)
        Text("num1:" + this.num1)
        Text("num2" + this.num2)
        Button("addNum1").onClick(() => {
          this.num1 += 1
        })
        Button("addNum2").onClick(() => {
          this.num2 += 1
        })
      }.width('100%')

    }.height('100%')

  }
}