HarmonyOS 能否自定义自己的装饰器？

Question

HarmonyOS 能否自定义自己的装饰器？

Answer 1

ArkTS支持TS5.0之前的TS装饰器语法。关于装饰器的定义和运行时行为，可以参考TS官方文档：https://www.typescriptlang.org/docs/handbook/decorators.html

function TestClassDecorator(target: Function) {
}
function TestMemberDecorator(target: testClass, memberName: String) {
}
function TestFunDecorator(target: testClass, propertyName: String, descriptor: PropertyDescriptor) {
}
function TestArgDecorator(target: Function, methodName: String, paramIndex: Number) {
}
@TestClassDecorator
class testClass {
  @TestMemberDecorator count: number = 123;
  @TestFunDecorator
  TestFun(@TestArgDecorator param: string) {
  }
}

注意，如果在ets文件中定义装饰器，则需要同时满足ArkTS的语法规则，比如不能使用any等。以下是类装饰器、属性装饰器、方法装饰器、参数装饰器的简单示例：

自定义装饰器不支持装饰struct，可参考demo：

// 类装饰器
function decorateKlass(target: ESObject) {
  console.log("decorateKlass")
}
@decorateKlass
class Person {
  age: number = 12
}
// 方法装饰器
export function MyDescriptor(target: Object, key: string, descriptor: PropertyDescriptor) {
  const originalMethod: Function = descriptor.value
  descriptor.value = (...args: Object[]) => {
    console.log(Calling ${target.constructor.name} method ${key} with argument: ${args})
    const result: Object = originalMethod(...args)
    console.log(Method ${key} returned: ${result})
    return result
  }
  return descriptor
}
@Entry
@Component
struct DecoratorDemo {
  @State message: string = 'Hello World';
  aboutToAppear() {
    this.demo()
  }
  build() {
    Flex() {
    }
    .backgroundColor(Color.Green)
    .constraintSize({
      minWidth: 100,
      maxWidth: 200,
      minHeight: 0,
      maxHeight: 200
    })
    .height('100%')
  }
  @MyDescriptor
  demo() {
    let person = new Person();
    return person.age
  }
}