ArkUI Subsystem ChangeLog

cl.arkui.1 Restrictions on Data Type Declarations of State Variables

1. The data types of state variables decorated by state decorators must be explicitly declared. They cannot be declared as any or Date.

   Example:

   // xxx.ets
   @Entry
   @Component
   struct DatePickerExample {
     // Incorrect: @State isLunar: any = false
     @State isLunar: boolean = false
     // Incorrect: @State selectedDate: Date = new Date('2021-08-08')
     private selectedDate: Date = new Date('2021-08-08')
   
     build() {
       Column() {
         Button('Switch Calendar')
           .margin({ top: 30 })
           .onClick(() => {
             this.isLunar = !this.isLunar
           })
         DatePicker({
           start: new Date('1970-1-1'),
           end: new Date('2100-1-1'),
           selected: this.selectedDate
         })
           .lunar(this.isLunar)
           .onChange((value: DatePickerResult) => {
             this.selectedDate.setFullYear(value.year, value.month, value.day)
             console.info('select current date is: ' + JSON.stringify(value))
           })
   
       }.width('100%')
     }
   }
   

   

2. The data type declaration of the @State, @Provide, @Link, or @Consume decorated state variables can consist of only one of the primitive data types or reference data types.

   The Length, ResourceStr, and ResourceColor types are combinations of primitive data types or reference data types. Therefore, they cannot be used by the aforementioned types of state variables. For details about the definitions of Length, ResourceStr, and ResourceColor, see Types.

   Example:

   // xxx.ets
   @Entry
   @Component
   struct IndexPage {
     // Incorrect: @State message: string | Resource = 'Hello World'
     @State message: string = 'Hello World'
     // Incorrect: @State message: ResourceStr = $r('app.string.hello')
     @State resourceStr: Resource = $r('app.string.hello')
   
     build() {
       Row() {
         Column() {
           Text(`${this.message}`)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   

   

Change Impacts

1. If the data type of a state variable decorated by a state decorator is declared as any, a build error will occur.

   // ArkTS:ERROR Please define an explicit type, not any.
   @State isLunar: any = false
   

2. If the data type of a state variable decorated by a state decorator is declared as Date, a build error will occur.

   // ArkTS:ERROR The @State property 'selectedDate' cannot be a 'Date' object.
   @State selectedDate: Date = new Date('2021-08-08')
   

3. If the data type of a @State, @Provide, @Link, and or @Consume decorated state variable is Length, ResourceStr, or ResourceColor, a build error will occur.

   /* ArkTS:ERROR The state variable type here is 'ResourceStr', it contains both a simple type and an object type,
     which are not allowed to be defined for state variable of a struct.*/
   @State message: ResourceStr = $r('app.string.hello')
   

Key API/Component Changes

N/A

Adaptation Guide

1. Explicitly declare the data type for state variables decorated by state decorators.

2. If a state variable decorated by a state decorator uses the Date object, change it to a regular variable – a variable not decorated by any decorator.

3. Adapt the @State, @Provide, @Link, and @Consume decorated variables based on the following code snippet so that they do not use the Length(string|number|Resource), ResourceStr(string|Resource), and ResourceColor(string|number|Color|Resource) types:

   // Incorrect:
   @State message: ResourceStr = $r('app.string.hello')
   // Corrected:
   @State resourceStr: Resource = $r('app.string.hello')
   

cl.arkui.2 Initialization Rules and Restrictions of Custom Components' Member Variables

Comply with the following rules when using constructors to initialize member variables:

NOTE

Supported (1): The dollar sign ($) must be used, for example, this.$varA.

regular: refers to a regular variable that is not decorated by any decorator.

@StorageLink, @StorageProp, @LocalStorageLink, and @LocalStorageProp variables cannot be initialized from the parent component.

Change Impacts

1. Variables decorated by @LocalStorageLink and @LocalStorageProp cannot be initialized from the parent component.

   @Entry
   @Component
   struct LocalStorageComponent {
       build() {
           Column() {
               Child({
                 /* ArkTS:ERROR Property 'simpleVarName' in the custom component 'Child' cannot
                   initialize here (forbidden to specify). */
                 simpleVarName: 1,
                 /* ArkTS:ERROR Property 'objectName' in the custom component 'Child' cannot
                   initialize here (forbidden to specify). */
                 objectName: new ClassA("x")
               })
           }
       }
   }
   @Component
   struct Child {
       @LocalStorageLink("storageSimpleProp") simpleVarName: number = 0;
       @LocalStorageProp("storageObjectProp") objectName: ClassA = new ClassA("x");
       build() {}
   }
   

2. The @ObjectLink decorated variable cannot be directly initialized from a decorated variable in the parent component. The source of the parent component must be an array item or object attribute decorated by @State, @Link, @Provide, @Consume, or @ObjectLink.

   let NextID : number = 0;
   
   @Observed class ClassA {
     public id : number;
     public c: number;
     constructor(c: number) {
       this.id = NextID++;
       this.c = c;
     }
   }
   
   @Component
   struct Child {
     @ObjectLink varA : ClassA;
     build() {
       Row() {
         Text('ViewA-' + this.varA.id)
       }
     }
   }
   
   @Component
   struct Parent {
     @Link linkValue: ClassA
     build() {
       Column() {
         /* ArkTS:ERROR The @Link property 'linkValue' cannot be assigned to
           the @ObjectLink property 'varA'.*/
         Child({ varA: this.linkValue })
       }
     }
   }
   

Key API/Component Changes

N/A

Adaptation Guide

1. When building a child component, do not perform the build on the variables decorated by @LocalStorageLink and @LocalStorageProp in the child component.

   To change these variables from the parent component, use the API provided by the LocalStorage (such as the set API) to assign values to them.

2. For details about how to use @ObjectLink, see @Observed and @ObjectLink.