MATLAB Programming Fundamentals - MathWorks

Change the Number of Inputs

This example shows how to set the number of inputs for a System object™ with and

without using getNumInputsImpl.

If you have a variable number of inputs or outputs and you intend to use the System

object in Simulink®, you must include the getNumInputsImpl or getNumOutputsImpl

method in your class definition.

These examples show modifications for the number of inputs. If you want to change the

number of outputs, the same principles apply.

As with all System object Impl methods, you always set the getNumInputsImpl and

getNumOutputsImpl method's access to protected because they are internal methods

that are never called directly.

Allow up to Three Inputs

This example shows how to write a System object that allows the number of inputs to

vary.

Update the stepImpl method to accept up to three inputs by adding code to handle one,

two, or three inputs. If you are only using this System object in MATLAB,

getNumInputsImpl and getNumOutputsImpl are not required.

Full Class Definition

classdef AddTogether < matlab.System

% Add inputs together

methods (Access = protected)

function y = stepImpl(~,x1,x2,x3)

switch nargin

case 2

y = x1;

case 3

y = x1 + x2;

case 4

y = x1 + x2 + x3;

otherwise

y = [];

end

34 System object Usage and Authoring