HarmonyOS 应用开发之自定义组件成员属性访问限定符使用限制-编程知识

ArkTS会对自定义组件的成员变量使用的访问限定符private/public/protected进行校验，当不按规范使用访问限定符private/public/protected时，会产生对应的日志信息。

说明：
从API version 12开始，支持自定义组件成员属性访问限定符使用限制的规则。

使用限制

对于@State/@Prop/@Provide/@BuilderParam/常规成员变量(不涉及更新的普通变量)，当使用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。
对于@StorageLink/@StorageProp/@LocalStorageLink/@LocalStorageLink/@Consume变量，当使用public修饰时，会有编译告警日志提示。
对于@Link/@ObjectLink变量，当使用private修饰时，会有编译告警日志提示。
由于struct没有继承能力，上述所有的这些变量使用protected修饰时，会有编译告警日志提示。
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。

错误使用场景示例

1.当成员变量被private访问限定符和@State/@Prop/@Provide/@BuilderParam装饰器同时修饰时，ArkTS会进行校验并产生告警日志。

@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)}}
}

编译告警日志如下：

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.

2.当成员变量被public访问限定符和@StorageLink/@StorageProp/@LocalStorageLink/@LocalStorageLink/@Consume装饰器同时修饰时，ArkTS会进行校验并产生告警日志。

@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)}}
}

编译告警日志如下：

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.

3.当成员变量被private访问限定符和@Link/@ObjectLink装饰器同时修饰时，ArkTS会进行校验并产生告警日志。

@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)}}
}

编译告警日志如下：

Property 'link_value' can not be decorated with both @Link and private.
Property 'objectLink_value' can not be decorated with both @ObjectLink and private.

4.当成员变量被protected访问限定符修饰时，ArkTS会进行校验并产生告警日志。

@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)}}
}

编译告警日志如下：

The member attributes of a struct can not be protected.

5.当成员变量被private访问限定符、@Require和@State/@Prop/@Provide/@BuilderParam装饰器同时修饰时，ArkTS会进行校验并产生告警日志。

@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)}}
}

编译告警日志如下：

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.

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