## Restrictions on Data Type Declarations of State Variables
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.
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).
| @Link | Not allowed| Allowed | Not recommended| Allowed |
| @Prop | Not allowed| Not allowed| Allowed | Allowed |
| @StorageLink | Not allowed| Allowed | Not allowed| Not allowed |
| @StorageProp | Not allowed| Not allowed| Not allowed| Allowed |
| Normal variable | Allowed | Not allowed| Not allowed| Allowed |
| **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 |
As indicated by the preceding table:
| **From the Variable in the Parent Component (Right) to the Variable in the Child Component (Below)**| **@StorageLink** | **@StorageProp** | **@LocalStorageLink** | **@LocalStorageProp** |
| **@Consume** | Not supported | Not supported | Not supported | Not supported |
| **@ObjectLink** | Not supported | Not supported | Not supported | Not supported |
> **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.
As indicated by the preceding tables:
- 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**.
- The normal variables of the parent component can be used to initialize the **@State** decorated variables of the child component, but not the **@Link** or **@Prop** decorated variables.
- The regular variables of the parent component can be used to initialize the **@State** variable of the child component, but cannot be used to initialize the **@Link**, **@Consume**, and **@ObjectLink** variables.
- The **@State**decorated variable of the parent component can be used to initialize the **@Prop**, **@Link** (using **$**), or normal variables of the child component, but not the **@State** decorated variables of the child component.
- The **@State**variable of the parent component can be used to initialize the **@Prop**, **@Link** (through **$**), or regular variables of the child component, but cannot be used to initialize the **@Consume** variable.
- The **@Link**decorated variables of the parent component can be used to initialize the **@Link** decorated or normal variables of the child component. However, initializing the **@State** decorated members of the child component can result in a syntax error. In addition, initializing the **@Prop** decorated variables is not recommended.
- The **@Link**variable of the parent component cannot be used to initialize the **@Consume** and **@ObjectLink** variables of the child component.
- The **@Prop**decorated variables of the parent component can be used to initialize the normal variables or **@Prop** decorated variables of the child component, but not the **@State** or **@Link** decorated variables.
- The **@Prop**variable of the parent component cannot be used to initialize the **@Consume** and **@ObjectLink** variables of the child component.
-Passing **@StorageLink** and **@StorageProp** from the parent component to the child component is prohibited.
-**@StorageLink**, **@StorageProp**, **@LocalStorageLink**, and **@LocalStorageProp** variables cannot be initialized from the parent component.
- In addition to the preceding rules, the TypeScript strong type rules need to be followed.
Example:
```ts
@Entry
@Component
structParent{
message:string="Hello World"
build(){
Column(){
Child({
stateMessage:this.message,
/* ArkTS:ERROR The regular property 'message' cannot be assigned
@@ -30,3 +30,5 @@ In the multi-dimensional state management mechanism for ArkUI, UI-related data c
-**@LocalStorageProp**: establishes one-way data binding between a component and the **LocalStorage**. Specifically, this is achieved by decorating the component's state variable with **@LocalStorageProp(*key*)**. Wherein, **key** is the attribute key value in the **LocalStorage**.
-**PersistentStorage**: provides a set of static methods for managing persistent data of applications. Persistent data with specific tags can be linked to the **AppStorage**, and then the persistent data can be accessed through the **AppStorage** APIs. Alternatively, the **@StorageLink** decorator can be used to access the variable that matches the specific key.
-**Environment**: provides the **AppStorage** with an array of environment state attributes that are required by the application and describe the device environment where the application runs. It is a singleton object created by the framework when the application is started.
For details about how to use state variables, see [Restrictions on Data Type Declarations of State Variables](arkts-restrictions-and-extensions.md).
