HarmonyOS 子组件被父组件包装后，如何通过父组件设置子组件的属性

import CustomSysComp, { MyTextInputModifier } from './CustomSysComp' 
 
@Entry 
@Component 
struct Index { 
 @Styles pressedStyles() { 
  .backgroundColor(Color.Blue) 
 } 
 build() { 
  Column() { 
   CustomSysComp({ 
    textInputModifier: new MyTextInputModifier() 
     .backgroundColor(Color.Blue) 
     .placeholderColor(Color.Red) 
   }) 
    .width("100%") 
    .height(400) 
  } 
  .width('100%') 
  .width('100%') 
 } 
}

@Component 
struct CustomSysComp { 
 
  // 设置自定义TextInput 
  textInputModifier: MyTextInputModifier = new MyTextInputModifier() 
  build() { 
    Column() { 
      TextInput({placeholder: "placeholder"}) 
        .attributeModifier(this.textInputModifier) 
      Button("button") 
    } 
    .width("100%") 
    .height("100%") 
  } 
} 
// 提供方创建自定类Class类，实现系统AttributeModifier接口 
export class MyTextInputModifier implements AttributeModifier<TextInputAttribute> { 
  // 默认属性 
  private mWidth: Length = '100%' 
  private mHeight: Length = 100 
  // 定制属性 
  private mPlaceholderColor: ResourceColor = Color.Gray 
  placeholderColor(placeholderColor: ResourceColor): MyTextInputModifier { 
    this.mPlaceholderColor = placeholderColor 
    return this 
  } 
  private mBackgroundColor: ResourceColor = Color.Orange 
  backgroundColor(backgroundColor: ResourceColor): MyTextInputModifier { 
    this.mBackgroundColor = backgroundColor 
    return this 
  } 
  applyNormalAttribute(instance: TextInputAttribute): void { 
    instance.width(this.mWidth) 
    instance.height(this.mHeight) 
    instance.placeholderColor(this.mPlaceholderColor) 
    instance.backgroundColor(this.mBackgroundColor) 
  } 
} 
export default CustomSysComp