- The dollar sign ($) is used to reference resources defined in the application. The format is as follows:
- $color:xxx
**Change Impacts**
If the verification rules are not met, an error is reported during compilation.
**Key API/Component Changes**
None
### Restrictions on Declaring Multiple Data Types of State Variables
If a **@State**, **@Provide**, **@Link**, or **@Consume** decorated state variable supports multiple data types, they must be all simple data types or references at one time.
When the defined state variable type contains both the simple data types and references, an error is reported during compilation.
**Key API/Component Changes**
If the defined state variable type contains both the simple data types and references, change the type to one of them, as shown in the preceding sample code.