matlab.System class

Base class for System objects

Description

matlab.System is the base class for System objects. In your class definition file, you must subclass your object from this base class (or from another class that derives from this base class). Subclassing allows you to use the implementation methods and service methods provided by this base class to build your object. Type this syntax as the first line of your class definition file to directly inherit from the matlab.System base class, where ObjectName is the name of your object:

classdef ObjectName < matlab.System

Note

You must set Access = protected for each matlab.System method you use in your code.

The matlab.System class is a handle class.

Class Attributes

`Abstract`	`true`
`HandleCompatible`	`true`
`StrictDefaults`	`false`

For information on class attributes, see Class Attributes.

Methods

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Authoring Methods (Protected)

Input Specification

`getNumInputsImpl`	Number of inputs to the System object
`isInputDataTypeMutableImpl`	Set whether System object input data type can change
`isInputSizeMutableImpl`	Set whether System object input size can change
`isInputComplexityMutableImpl`	Set whether System object input complexity can change
`isInputDirectFeedthroughImpl`	Direct feedthrough status of input
`getInputDimensionConstraintImpl`	Define input dimension constraints for dataflow subsystems

Output Specification

`getNumOutputsImpl`	Number of outputs from System object
`getOutputDataTypeImpl`	Data types of output ports
`getOutputSizeImpl`	Sizes of output ports
`isOutputComplexImpl`	Complexity of output ports
`isOutputFixedSizeImpl`	Fixed- or variable-size output ports
`getOutputDimensionConstraintImpl`	Define output dimension constraints for dataflow subsystems

State Specification

`getDiscreteStateSpecificationImpl`	Discrete state size, data type, and complexity
`isDiscreteStateSpecificationMutableImpl`	Control whether discrete states can change data type
`getDiscreteStateImpl`	Discrete state property values

Sample Time Specification

`getSampleTimeImpl`	Specify sample time type, offset time, and sample time
`allowModelReferenceDiscreteSampleTimeInheritanceImpl`	Model reference sample time inheritance status for discrete sample times

Interface Specification

`getGlobalNamesImpl`	Global variable names for MATLAB System block
`getInterfaceImpl` (Simulink)	Set System object as message or data
`isTunablePropertyDataTypeMutableImpl`	Set whether tunable properties can change data type
`isDoneImpl`	End-of-data flag
`getSimulateUsingImpl`	Specify value for Simulate using parameter
`getSimulinkFunctionNamesImpl`	Register Simulink function names used in your System object
`showFiSettingsImpl`	Fixed point data type tab visibility for System objects
`supportsMultipleInstanceImpl`	Support System object in Simulink For Each subsystem
`getImpulseResponseLengthImpl`	Define length of input effects for dataflow subsystems

Dialog and Appearance

`getPropertyGroupsImpl`	Property groups for System object display
`showSimulateUsingImpl`	Visibility of Simulate using parameter
`getIconImpl`	Name to display as block icon
`getHeaderImpl`	Header for System object display
`getInputNamesImpl`	Names of MATLAB System block input ports
`getOutputNamesImpl`	Names of MATLAB System block output ports
`isInactivePropertyImpl`	Status of inactive property

Simulation Methods

`setupImpl`	Initialize System object
`stepImpl`	System output and state update equations
`resetImpl`	Reset System object states
`releaseImpl`	Release resources
`processTunedPropertiesImpl`	Action when tunable properties change
`validatePropertiesImpl`	Validate property values of System object
`processInputSpecificationChangeImpl`	Perform actions when input size, complexity, or data type change
`validateInputsImpl`	Validate inputs to System object
`updateImpl`	Update object states based on inputs

Clone, Save and Load

`loadObjectImpl`	Load System object from MAT file
`saveObjectImpl`	Save System object in MAT file

Help

infoImpl Information about System object

Query Functions (Protected)

Functions for Implementing Authoring Methods

`setProperties`	Set property values using name-value pairs when creating System object
`propagatedInputComplexity`	Complexity of input during Simulink propagation
`propagatedInputDataType`	Data type of input during Simulink propagation
`propagatedInputFixedSize`	Fixed-size status of input during Simulink propagation
`propagatedInputSize`	Size of input during Simulink propagation
`createSampleTime`	Create sample time specification object
`getSampleTime`	Query sample time
`getCurrentTime`	Current simulation time in MATLAB System block
`setNumTicksUntilNextHit` (Simulink)	Set the number of ticks in Simulink sample time
`displayScalarObject`	Display format for scalar objects
`getHeader`	Build and return display header text
`getFooter`	Build and return display footer text

Implementation Methods (Public)

Methods for Implementing System Objects

`nargin`	Number of input arguments for System object
`nargout`	Number of output arguments for System object
`getNumInputs`	Number of inputs required to call the System object
`getNumOutputs`	Number of outputs from calling the System object
`setup`	One-time set up tasks for System objects
`reset`	Reset internal states of System object
`step`	Run System object algorithm
`release`	Release resources and allow changes to System object property values and input characteristics
`clone`	Create duplicate System object
`isDone`	End-of-data status
`isLocked`	Determine if System object is in use

Examples

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Create Basic System Object

Open Live Script

This example shows how to author a basic System object called AddOne.

In MATLAB, select New > System object > Basic. A new editor window opens with default syntax and comments for a new System object.

Rename the class AddOne. Modify the default template so your class looks like this:

classdef AddOne < matlab.System
% ADDONE Compute an output value that increments the input by one

    methods (Access = protected)
       % Implement algorithm. Calculate y as a function of input x.
       function y = stepImpl(~,x)
          y = x + 1;
       end    
    end
end

Use this object by creating an instance of AddOne and running the object with input.

addingObject = AddOne;
x = 5;
addingObject(x)

ans = 6

More About

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Attributes

You can apply attributes to the System object™ class and properties. To learn more about attributes, see Class Attributes or Property Attributes.

Class Attribute

This table shows attributes that you can apply to the MATLAB^® System object class.

Attribute Name Description

StrictDefaults

Control the defaults for the methods that restrict specification modifications changes:

isInputSizeMutableImpl
isInputComplexityMutableImpl
isInputDataTypeMutableImpl
isTunablePropertyDataTypeMutableImpl
isDiscreteStateSpecificationMutableImpl

By default, these methods return true. When you add this class attribute, these methods return false by default. By making these methods return false, the specified aspects of the inputs, tunable properties, or discrete states cannot change. You can always implement these methods individually. Customized methods take precedence over the StrictDefaults attribute.

For System objects used in Simulink^®, this attribute only restricts input size changes because Simulink already restricts complexity and data type for tunable properties, inputs, and states.

Specify the class attribute value in parentheses followed by the class name, for example:

classdef (StrictDefaults) MySystemObject < matlab.System

Property Attributes

You can apply the following attributes to any property of a custom System object.

Nontunable Use Nontunable to prevent changes to a property value while the object is in use. By default, all properties are tunable. The Nontunable attribute is useful to lock down a property that has side effects when changed. This attribute is also useful for locking a property value assumed to be constant during processing. You should always specify properties that affect the number of input or output ports as Nontunable.

DiscreteState Use DiscreteState to mark a property so it will display its state value when you use the getDiscreteState method.

Version History

Introduced in R2011b