Customize Enumerated Types in Generated Code

For code generation, to customize an enumeration, in the static methods section of the class definition, include customized versions of the methods listed in this table.

Method	Description	Default Value Returned or Specified	When to Use
`getDefaultValue`	Returns the default enumerated value.	First value in the enumeration class definition.	For a default value that is different than the first enumeration value, provide a `getDefaultValue` method that returns the default value that you want. See Specify a Default Enumeration Value.
`getHeaderFile`	Specifies the file that defines an externally defined enumerated type.	`''`	To use an externally defined enumerated type, provide a `getHeaderFile` method that returns the path to the header file that defines the type. In this case, the code generator does not produce the class definition. See Specify a Header File
`addClassNameToEnumNames`	Specifies whether the class name becomes a prefix in the generated code.	`false` — prefix is not used.	If you want the class name to become a prefix in the generated code, set the return value of the `addClassNameToEnumNames` method to `true`. See Include Class Name Prefix in Generated Enumerated Type Value Names. Note When generating enumeration classes (C++11 and newer standards), the code generator ignores this static method.
`generateEnumClass`	Specifies whether to generate enumeration classes	`true` — enumeration classes are generated in C++ code	When generating C++11 (or newer) code, to instruct the code generator to produce an ordinary C enumeration for a particular MATLAB^® enumeration, set the return value of the `generateEnumClass` method to `false`. See Generate C++ Code That Contains Ordinary C Enumeration.

Specify a Default Enumeration Value

If the value of a variable that is cast to an enumerated type does not match one of the enumerated type values:

Generated MEX reports an error.
Generated C/C++ code replaces the value of the variable with the enumerated type default value.

Unless you specify otherwise, the default value for an enumerated type is the first value in the enumeration class definition. To specify a different default value, add your own getDefaultValue method to the methods section. In this example, the first enumeration member value is LEDcolor.GREEN, but the getDefaultValue method returns LEDcolor.RED:

classdef LEDcolor < int32
    enumeration
        GREEN(1),
        RED(2)
    end
    
    methods (Static)
        function y = getDefaultValue()
            y = LEDcolor.RED;
        end
    end
end

Specify a Header File

To specify that an enumerated type is defined in an external file, provide a customized getHeaderFile method. This example specifies that LEDcolor is defined in the external file my_LEDcolor.h.

classdef LEDcolor < int32
    enumeration
        GREEN(1),
        RED(2)
    end

    methods(Static)
      function y=getHeaderFile()
        y='my_LEDcolor.h';
      end
    end
end

You must provide my_LEDcolor.h. For example:

enum LEDcolor
{
    GREEN = 1,
    RED
};
typedef enum LEDcolor LEDcolor;

If you place the MATLAB enumeration LEDcolor inside the MATLAB namespace nmsp and generate C++ code, code generation preserves the name of this enumeration and places it inside the C++ namespace nmsp in the generated code. Therefore, in the header file that you provide, you must define this enumeration inside the namespace nmsp.

Include Class Name Prefix in Generated Enumerated Type Value Names

By default, the generated enumerated type value name does not include the class name prefix. For example:

enum LEDcolor
{
    GREEN = 1,
    RED
};

typedef enum LEDcolor LEDcolor;

To include the class name prefix, provide an addClassNameToEnumNames method that returns true. For example:

classdef LEDcolor < int32
    enumeration
        GREEN(1),
        RED(2)
    end

    methods(Static)
      function y = addClassNameToEnumNames()
        y=true;
      end
    end
end

In the generated type definition, the enumerated value names include the class prefix LEDcolor.

enum LEDcolor
{
    LEDcolor_GREEN = 1,
    LEDcolor_RED
};

typedef enum LEDcolor LEDcolor;

Generate C++ Code That Contains Ordinary C Enumeration

When you generate code using a language standard that supports enumeration classes (C++11 or newer), your MATLAB enumeration class is converted to an enumeration class. For example:

enum class MyEnumClass16 : short
{
  Orange = 0, // Default value
  Yellow,
  Pink
};

To generate an ordinary C enumeration instead, provide a generateEnumClass method that returns false. For example:

classdef MyEnumClass16 < int16
    enumeration
        Orange(0),
        Yellow(1),
        Pink(2)
    end

    % particular enum opting out
    methods(Static)
        function y = generateEnumClass()
            y = false;   
        end
    end
end

Now the generated code contains an ordinary C enumeration.

enum MyEnumClass16 : short
{
  Orange = 0, // Default value
  Yellow,
  Pink
};