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Define Enumerated Data Types

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.

Before you can add enumerated data to a Stateflow chart, you must define an enumerated data type in a MATLAB® class definition file. Create a different file for each enumerated type.

Elements of an Enumerated Data Type Definition

The enumerated data type definition consists of three sections of code.

Section of CodeRequired?Purpose
classdef

Yes

Provides the name of the enumerated data type

enumeration

Yes

Lists the enumerated values that the data type allows

methods

No

Provides methods that customize the data type

Define an Enumerated Data Type

  1. Open a new file in which to store the data type definition. From the Home tab on the MATLAB toolstrip, select New > Class.

  2. Complete the classdef section of the definition.

    classdef BasicColors < Simulink.IntEnumType
      ...
    end

    The classdef section defines an enumerated data type with the name BasicColors. Stateflow derives the data type from the built-in type Simulink.IntEnumType. The enumerated data type name must be unique among data type names and workspace variable names.

  3. Define enumerated values in an enumeration section.

    classdef BasicColors < Simulink.IntEnumType
      enumeration
        Red(0)
        Yellow(1)
        Green(2)
      end
    end

    An enumerated type can define any number of values. The enumeration section lists the set of enumerated values that this data type allows. Each enumerated value consists of a name and an underlying integer value. Each name must be unique within its type, but can also appear in other enumerated types. The default value is the first one in the list, unless you specify otherwise in the methods section of the definition.

  4. (Optional) Customize the data type by using a methods section. The section can contain these methods:

    • getDefaultValue specifies a default enumerated value other than the first one in the list of allowed values.

    • getDescription specifies a description of the data type for code generated by Simulink Coder™.

    • getHeaderFile specifies custom header file that contains the enumerated type definition in code generated by Simulink Coder.

    • getDataScope enables exporting or importing the enumerated type definition to or from a header file in code generated by Simulink Coder.

    • addClassNameToEnumNames enhances readability and prevents name conflicts with identifiers in code generated by Simulink Coder.

    For example, this MATLAB file presents a customized definition for the enumerated data type BasicColors that:

    • Specifies that the default enumerated value is the last one in the list of allowed values.

    • Includes a short description of the data type for code generated by Simulink Coder.

    • Imports the definition of the data type from a custom header file to prevent Simulink Coder from generating the definition.

    • Adds the name of the data type as a prefix to each enumeration member name in code generated by Simulink Coder.

    classdef BasicColors < Simulink.IntEnumType
      enumeration
        Red(0)
        Yellow(1)
        Green(2)
      end
    
      methods (Static = true)
        function retVal = getDefaultValue()
          % GETDEFAULTVALUE Specifies the default enumeration member.
          % Return a valid member of this enumeration class to specify the default.
          % If you do not define this method, Simulink uses the first member.
          retVal = BasicColors.Green;
        end
    
        function retVal = getDescription()
          % GETDESCRIPTION Specifies a string to describe this enumerated type.
          retVal = 'This defines an enumerated type for colors';
        end
    
        function retVal = getHeaderFile()
          % GETHEADERFILE Specifies the file that defines this type in generated code.
          % The method getDataScope determines the significance of the specified file.
          retVal = 'imported_enum_type.h';
        end
    
        function retVal = getDataScope()
          % GETDATASCOPE Specifies whether generated code imports or exports this type.
          % Return one of these strings:
          % 'Auto':     define type in model_types.h, or import if header file specified
          % 'Exported': define type in a generated header file
          % 'Imported': import type definition from specified header file
          % If you do not define this method, DataScope is 'Auto' by default.
          retVal = 'Imported';
        end
    
        function retVal = addClassNameToEnumNames()
          % ADDCLASSNAMETOENUMNAMES Specifies whether to add the class name
          % as a prefix to enumeration member names in generated code.
          % Return true or false.
          % If you do not define this method, no prefix is added.
          retVal = true;
        end % function
      end % methods
    end % classdef

  5. Save the file on the MATLAB path. The name of the file must match exactly the name of the data type. For example, the definition for the data type BasicColors must reside in a file named BasicColors.m.

    Tip

    To add a folder to the MATLAB search path, type addpath pathname at the command prompt.

Specify Data Type in the Property Inspector

When you add enumerated data to your chart, specify its type in the Property Inspector.

  1. In the Type field, select Enum: <class name>.

  2. Replace <class name> with the name of the data type. For example, you can enter Enum: BasicColors in the Type field.

  3. (Optional) Enter an initial value for the enumerated data by using a prefixed identifier. The initial value must evaluate to a valid MATLAB expression.

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