Define Data Classes

This example shows how to subclass Simulink® data classes.

Use MATLAB® class syntax to create a data class in a package. Optionally, assign properties to the data class and define storage classes.

Use an example to define data classes

Open Script

  1. In the working folder, view the +SimulinkDemos data class package in the folder dataclasses.

  2. Copy the folder to the location where you want to define your data classes.

  3. Rename the folder +mypkg and add its parent folder to the MATLAB path.

  4. Modify the data class definitions.

Manually define data class

  1. Create a package folder +mypkg and add its parent folder to the MATLAB path.

  2. Create class folders @Parameter and @Signal inside +mypkg.

    Note

    Simulink requires data classes to be defined inside +Package/@Class folders.

  3. In the @Parameter folder, create a MATLAB file Parameter.m and open it for editing.

  4. Define a data class that is a subclass of Simulink.Parameter using MATLAB class syntax.

    classdef Parameter < Simulink.Parameter
   
end % classdef

To use a custom class name other than Parameter or Signal, name the class folders using the custom name. For example, to define a class mypkg.myParameter:

  • Define the data class as a subclass of Simulink.Parameter or Simulink.Signal.

    classdef myParameter < Simulink.Parameter
   
end % classdef

  • In the class definition, name the constructor method as myParameter or mySignal.

  • Name the class folder, which contains the class definition, as @myParameter or @mySignal.

Optional: Add properties to data class

The properties and end keywords enclose a property definition block.

classdef Parameter < Simulink.Parameter
	properties % Unconstrained property type
		Prop1 = [];
	end

	properties(PropertyType = 'logical scalar')
		Prop2 = false;
	end

	properties(PropertyType = 'char')
		Prop3 = '';
	end

	properties(PropertyType = 'char',...
      AllowedValues = {'red'; 'green'; 'blue'})
		Prop4 = 'red';
	end
end % classdef

If you add properties to a subclass of Simulink.Parameter, Simulink.Signal, or Simulink.CustomStorageClassAttributes, you can specify the following property types.

Property TypeSyntax
Double numberproperties(PropertyType = 'double scalar')
int32 numberproperties(PropertyType = 'int32 scalar')
Logical numberproperties(PropertyType = 'logical scalar')
Character vector (char)properties(PropertyType = 'char')
Character vector with limited set of allowed valuesproperties(PropertyType = 'char', AllowedValues = {'a', 'b', 'c'})

If you add a property that requires special copy behavior, you define that behavior by overriding the copyElement method. For example, in the +SimulinkDemos data class package, the class definition file Parameter.m defines the property GenericProperty with an unconstrained property type. The copyElement method specifies the copy behavior for GenericProperty. When you add, remove, or change a property that requires special copy behavior, you must also be sure to update the copyElement method.

If you use MATLAB property validation (see Validate Property Values) instead of PropertyType, the properties are displayed as an edit field in the property dialog box of the class. If you use PropertyType and AllowedValues, then the property dialog box displays:

  • A check box for logical scalar properties.

  • A dropdown menu for character vectors and AllowedValues.

Optional: Add initialization code to data class

You can add a constructor within your data class to perform initialization activities when the class is instantiated. The added constructor cannot require an input argument.

In this example, the constructor initializes the value of object obj based on an optional input argument.

classdef Parameter < Simulink.Parameter
	methods
		function obj = Parameter(optionalValue)
			if (nargin == 1)
				obj.Value = optionalValue;
			end
		end
	end % methods
end % classdef

Optional: Define storage classes

Use the setupCoderInfo method to configure the CoderInfo object of your class. Then, create a call to the useLocalCustomStorageClasses method and open the Custom Storage Class Designer.

  1. In the constructor within your data class, call the useLocalCustomStorageClasses method.

    classdef Parameter < Simulink.Parameter
	methods
		function setupCoderInfo(obj)
			useLocalCustomStorageClasses(obj, 'mypkg');
			
			obj.CoderInfo.StorageClass = 'Custom';
		end
	end % methods
end % classdef

  2. Open the Custom Storage Class Designer for your package.

    cscdesigner('mypkg')

  3. Define storage classes.

Optional: Define custom attributes for storage classes

  1. Create a MATLAB file myCustomAttribs.m and open it for editing. Save this file in the +mypkg/@myCustomAttribsfolder, where +mypkg is the folder containing the @Parameter and @Signal folders.

  2. Define a subclass of Simulink.CustomStorageClassAttributes using MATLAB class syntax. For example, consider a storage class that defines data using the original identifier but also provides an alternate name for the data in generated code.

    classdef myCustomAttribs < Simulink.CustomStorageClassAttributes
	properties(PropertyType = 'char')
		AlternateName = '';
	end
end % classdef

  3. Override the default implementation of the isAddressable method to determine whether the storage class is writable.

    classdef myCustomAttribs < Simulink.CustomStorageClassAttributes
		properties(PropertyType = 'logical scalar')
			IsAlternateNameInstanceSpecific = true;
		end
		
		methods
			function retVal = isAddressable(hObj, hCSCDefn, hData)
				retVal = false;
			end
		end % methods
end % classdef

  4. Override the default implementation of the getInstanceSpecificProps method.

    For example, see these override functions:

    function props = getInstanceSpecificProps(hObj)
    % GETINSTANCESPECIFICPROPERTIES  Return instance-specific properties
    %   (custom attributes that can be modified on each data object).
        
      if hObj.IsStructNameInstanceSpecific
        props = findprop(hObj, 'StructName');
      else
        props = [];
      end
    end
    function props = getInstanceSpecificProps(hObj)
    % GETINSTANCESPECIFICPROPERTIES  Return instance-specific properties
    %   (custom attributes that can be modified on each data object).
      props = [];
      
      if hObj.IsOwnerInstanceSpecific
          ptmp = findprop(hObj, 'Owner');
          props = [props; ptmp];
      end
      
      if hObj.IsDefinitionFileInstanceSpecific
          ptmp = findprop(hObj, 'DefinitionFile');
          props = [props; ptmp];
      end
      
      if hObj.IsPersistenceLevelInstanceSpecific
          ptmp = findprop(hObj, 'PersistenceLevel');
          props = [props; ptmp];
      end
    end

    Note

    This is an optional step. By default, all custom attributes are instance-specific and are modifiable for each data object. However, you can limit which properties are allowed to be instance-specific.

  5. Override the default implementation of the getIdentifiersForInstance method to define identifiers for objects of the data class.

    Note

    In its default implementation, this method queries the name or identifier of the data object and uses that identifier in generated code. By overriding this method, you can control the identifier of your data objects in generated code.

    classdef myCustomAttribs < Simulink.CustomStorageClassAttributes
	properties(PropertyType = 'char')
		GetFunction = '';
		SetFunction = '';
	end
 
	methods
		function retVal = getIdentifiersForInstance(hCSCAttrib,...
 hCSCDefn, hData, identifier)
			retVal = struct('GetFunction',...
 hData.CoderInfo.CustomAttributes.GetFunction, ...
			'SetFunction', hData.CoderInfo.CustomAttributes.SetFunction);
		end%
	end % methods
end % classdef

  6. If you are using grouped storage classes, override the default implementation of the getIdentifiersForGroup method to specify the identifier for the group in generated code.

    For an example, in the working folder, see CSCTypeAttributes_FlatStructure.m in the folder @CSCTypeAttributes_FlatStructure.

See Also

Topics