鸿蒙Next自定义组件属性访问限定符

在鸿蒙Next开发中，ArkTS对自定义组件的成员变量使用的访问限定符private/public/protected有特定的校验规则，当不按规范使用时会产生相应的日志信息。

一、使用限制概述

（一）private修饰相关限制

对于@State/@prop/@Provide/@BuilderParam/常规成员变量（不涉及更新的普通变量），使用private修饰时，在自定义组件构造时不允许进行赋值传参，否则会有编译告警日志提示。 ### （二）public修饰相关限制
对于@StorageLink/@StorageProp/@LocalStorageLink/@LocalStorageProp/@Consume变量，使用public修饰时，会有编译告警日志提示。 ### （三）private与特定装饰器同时修饰限制
对于@Link/@ObjectLink变量，使用private修饰时，会有编译告警日志提示。 ### （四）protected修饰限制
由于struct没有继承能力，所有上述变量使用protected修饰时，会有编译告警日志提示。 ### （五）@Require与private同时修饰限制
当@Require和private同时修饰自定义组件struct的@State/@prop/@Provide/@BuilderParam/常规成员变量（不涉及更新的普通变量）时，会有编译告警日志提示。

二、错误使用场景示例

（一）private与@State/@prop/@Provide/@BuilderParam同时修饰

代码示例

@Entry
@Component
struct AccessRestrictions {
  @Builder
  buildTest() {
    Text("Parent builder")
  }
  build() {
    Column() {
      ComponentsChild({
        state_value: "Hello",
        prop_value: "Hello",
        provide_value: "Hello",
        builder_value: this.buildTest,
        regular_value: "Hello"
      })
    }
  .width('100%')
  }
}
@Component
struct ComponentsChild {
  @State private state_value: string = "Hello";
  @Prop private prop_value: string = "Hello";
  @Provide private provide_value: string = "Hello";
  @BuilderParam private builder_value: () => void = this.buildTest;
  private regular_value: string = "Hello";
  @Builder
  buildTest() {
    Text("Child builder")
  }
  build() {
    Column() {
      Text("Hello")
      .fontSize(50)
      .fontWeight(FontWeight.Bold)
    }
  }
}

编译告警日志
- Property'state_value' is private and can not be initialized through the component constructor.
- Property 'prop_value' is private and can not be initialized through the component constructor.
- Property 'provide_value' is private and can not be initialized through the component constructor.
- Property 'builder_value' is private and can not be initialized through the component constructor.
- Property'regular_value' is private and can not be initialized through the component constructor.

（二）public与@StorageLink/@StorageProp/@LocalStorageLink/@LocalStorageProp/@Consume同时修饰

代码示例

@Entry
@Component
struct AccessRestrictions {
  @Provide consume_value: string = "Hello";
  build() {
    Column() {
      ComponentChild()
    }
  .width('100%')
  }
}
@Component
struct ComponentChild {
  @LocalStorageProp("sessionLocalProp") public local_prop_value: string = "Hello";
  @LocalStorageLink("sessionLocalLink") public local_link_value: string = "Hello";
  @StorageProp("sessionProp") public storage_prop_value: string = "Hello";
  @StorageLink("sessionLink") public storage_link_value: string = "Hello";
  @Consume public consume_value: string;
  build() {
    Column() {
      Text("Hello")
      .fontSize(50)
      .fontWeight(FontWeight.Bold)
    }
  }
}

编译告警日志
- Property 'local_prop_value' can not be decorated with both @LocalStorageProp and public.
- Property 'local_link_value' can not be decorated with both @LocalStorageLink and public.
- Property'storage_prop_value' can not be decorated with both @StorageProp and public.
- Property'storage_link_value' can not be decorated with both @StorageLink and public.
- Property 'consume_value' can not be decorated with both @Consume and public.

（三）private与@Link/@ObjectLink同时修饰

代码示例

@Entry
@Component
struct AccessRestrictions {
  @State link_value: string = "Hello";
  @State objectLink_value: ComponentObj = new ComponentObj();
  build() {
    Column() {
      ComponentChild({link_value: this.link_value, objectLink_value: this.objectLink_value})
    }
  .width('100%')
  }
}
@Observed
class ComponentObj {
  count: number = 0;
}
@Component
struct ComponentChild {
  @Link private link_value: string;
  @ObjectLink private objectLink_value: ComponentObj;
  build() {
    Column() {
      Text("Hello")
      .fontSize(50)
      .fontWeight(FontWeight.Bold)
    }
  }
}

编译告警日志
- Property 'link_value' can not be decorated with both @link and private.
- Property 'objectLink_value' can not be decorated with both @ObjectLink and private.

（四）protected修饰

代码示例

@Entry
@Component
struct AccessRestrictions {
  build() {
    Column() {
      ComponentChild({regular_value: "Hello"})
    }
  .width('100%')
  }
}
@Component
struct ComponentChild {
  protected regular_value: string = "Hello";
  build() {
    Column() {
      Text("Hello")
      .fontSize(50)
      .fontWeight(FontWeight.Bold)
    }
  }
}

编译告警日志
- The member attributes of a struct can not be protected.

（五）private、@Require与@State/@prop/@Provide/@BuilderParam同时修饰

代码示例

@Entry
@Component
struct AccessRestrictions {
  build() {
    Column() {
      ComponentChild({prop_value: "Hello"})
    }
  .width('100%')
  }
}
@Component
struct ComponentChild {
  @Require @Prop private prop_value: string = "Hello";
  build() {
    Column() {
      Text("Hello")
      .fontSize(50)
      .fontWeight(FontWeight.Bold)
    }
  }
}

编译告警日志
- Property 'prop_value' can not be decorated with both @Require and private.
- Property 'prop_value' is private and can not be initialized through the component constructor.

开发者在使用鸿蒙Next自定义组件时，需遵循这些访问限定符的使用规则，避免因不规范使用而产生编译告警，确保组件的正确构建和功能实现。同时，注意这些规则从API version 12开始支持，在开发过程中要根据实际的API版本进行相应的处理。