Best Practices for Using Enumerated Data
To enhance the readability of a Stateflow® chart, use enumerated data. With enumerated data, you can:
Create a restricted set of values and refer to those values by name.
Group related values into separate data types.
Avoid defining a long list of constants.
Enumerated data is supported in Stateflow charts in Simulink® models. For more information, see Reference Values by Name by Using Enumerated Data.
Guidelines for Defining Enumerated Data Types
Use Unique Name for Each Enumerated Type
To avoid name conflicts, the name of an enumerated data type cannot match the name of:
Another data type
A data object in the Stateflow chart
A variable in the MATLAB® base workspace
Use Same Name for Enumerated Type and Class Definition File
To enable resolution of enumerated data types for Simulink models, the name of the MATLAB file that contains the type definition must match the name of the data type.
Apply Changes in Enumerated Type Definition
When you update an enumerated data type definition for an open model, the changes do not take effect immediately. To see the effects of updating a data type definition:
Save and close the model.
Delete all instances of the data type from the MATLAB base workspace. To find these instances, type
whosat the command prompt.
Open the model and start simulation or generate code by using Simulink Coder™.
Guidelines for Referencing Enumerated Data
Ensure Unique Name Resolution for Nonprefixed Identifiers
If you use nonprefixed identifiers to refer to enumerated values in a chart, ensure that each enumerated name belongs to a unique enumerated data type.
Use Unique Identifiers for Enumerated Values
If an enumerated value uses the same identifier as a data object or a bus field, the
chart does not resolve the identifier correctly. For example, this diagram shows the
stages in which a chart tries to resolve the identifier
Set Initial Values of Enumerated Data by Using Prefixed Identifiers
If you choose to set an initial value for enumerated data, you must use a prefixed
identifier in the Initial value field of the Property
Inspector. For example,
BasicColors.Red is a valid
Red is not. The initial value must evaluate to a valid
Enhance Readability of Generated Code by Using Prefixed Identifiers
If you add prefixes to enumerated names in the generated code, you enhance readability and avoid name conflicts with global symbols. For details, see Use Enumerated Data in Generated Code (Simulink Coder).
Guidelines and Limitations for Enumerated Data
Do Not Enter Minimum or Maximum Values for Enumerated Data
For enumerated data, leave the Minimum and Maximum properties empty. The chart ignores any values that you enter for these properties.
Whether these fields appear in the Property Inspector depends on which Type field option you use to define enumerated data.
|Type Field Option||Appearance of the Minimum and Maximum Fields|
Do Not Assign Enumerated Values to Constant Data
Because enumerated values are constants, assigning these values to constant data is redundant and unnecessary. If you try to assign enumerated values to constant data, an error appears.
Do Not Use
ml Namespace Operator to Access Enumerated Data
ml operator does not support enumerated data.
Do Not Define Enumerated Data at Machine Level of Hierarchy
Machine-parented data is not supported for enumerated types.