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](../../../application-dev/reference/arkui-ts/ts-types.md).
1. If the data type of a state variable decorated by a state decorator is declared as **any**, a build error will occur.
```ts
// ArkTS:ERROR Please define an explicit type, not any.
@StateisLunar: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.
```ts
// ArkTS:ERROR The @State property 'selectedDate' cannot be a 'Date' object.
@StateselectedDate:Date=newDate('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.
```ts
/* 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.*/
@Statemessage:ResourceStr=$r('app.string.hello')
```
**Key API/Component Changes**
N/A
**Adaptation Guide**
1. Explicitly declare the data type for state variables decorated by state decorators.
2. If a state variable decorated by a state decorator uses the **Date** object, change it to a regular variable – a variable not decorated by any decorator.
3.
Adapt the **@State**, **@Provide**, **@Link**, and **@Consume** decorated variables based on the following code snippet so that they do not use the **Length(string|number|Resource)**, **ResourceStr(string|Resource)**, and **ResourceColor(string|number|Color|Resource)** types:
```ts
// Incorrect:
@Statemessage:ResourceStr=$r('app.string.hello')
// Corrected:
@StateresourceStr: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:
| **From the Variable in the Parent Component (Right) to the Variable in the Child Component (Below)**| **regular** | **@State** | **@Link** | **@Prop** | **@Provide** | **@Consume** | **@ObjectLink** |
| **@Consume** | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported |
| **@ObjectLink** | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported | Not supported |
| **From the Variable in the Parent Component (Right) to the Variable in the Child Component (Below)**| **@StorageLink** | **@StorageProp** | **@LocalStorageLink** | **@LocalStorageProp** |
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**.
```ts
letNextID:number=0;
@ObservedclassClassA{
publicid:number;
publicc:number;
constructor(c:number){
this.id=NextID++;
this.c=c;
}
}
@Component
structChild{
@ObjectLinkvarA:ClassA;
build(){
Row(){
Text('ViewA-'+this.varA.id)
}
}
}
@Component
structParent{
@LinklinkValue: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](../../../application-dev/quick-start/arkts-state-mgmt-page-level.md).
## cl.arkui.3 Change of the onScrollBegin Event of the \<List> and \<Scroll> Components
The **onScrollBegin** event of the **\<List>** and **\<Scroll>** components is renamed **onScrollFrameBegin**. In the **onScrollBegin** event, the amount to scroll by is indicated by the **dx** and **dy** parameters. In the **onScrollFrameBegin** event, it is indicated by the **offset** parameter. The **onScrollFrameBegin** event adds the **ScrollState** parameter to indicate whether the component is in the finger dragging or inertial scrolling state.
**Change Impacts**
The **onScrollBegin** event is deprecated and must be replaced with the **onScrollFrameBegin** event.
Switch the event from **onScrollBegin** to **onScrollFrameBegin**, and use the **offset** parameter in **onScrollFrameBegin**, rather than the **dx** and **dy** parameters in **onScrollBegin**, to indicate the amount to scroll by.
Example of using the **onScrollBegin** event:
```ts
@Entry
@Component
structNestedScroll{
@StatelistPosition:number=0;// 0 indicates scrolling to the top of the list, 1 indicates scrolling to the middle of the list, and 2 indicates scrolling to the bottom of the list.
Example of using the **onScrollFrameBegin** event:
```ts
@Entry
@Component
structNestedScroll{
@StatelistPosition:number=0;// 0 indicates scrolling to the top of the list, 1 indicates scrolling to the middle of the list, and 2 indicates scrolling to the bottom of the list.
