MATLAB Programming Fundamentals - MathWorks

Use Global Variables in System Objects

Global variables are variables that you can access in other MATLAB functions or Simulink

blocks.

System Object Global Variables in MATLAB

For System objects that are used only in MATLAB, you define global variables in System

object class definition files in the same way that you define global variables in other

MATLAB code (see “Global Variables” on page 20-13).

System Object Global Variables in Simulink

For System objects that are used in the MATLAB System block in Simulink, you also

define global variables as you do in MATLAB. However, to use global variables in

Simulink, you must declare global variables in the stepImpl, updateImpl, or

outputImpl method if you have declared them in methods called by stepImpl,

updateImpl, or outputImpl, respectively.

You set up and use global variables for the MATLAB System block in the same way as you

do for the MATLAB Function block (see “Data Stores” (Simulink) and “Share Data

Globally” (Simulink)). Like the MATLAB Function block, you must also use variable name

matching with a Data Store Memory block to use global variables in Simulink.

For example, this class definition file defines a System object that increments the first row

of a matrix by 1 at each time step. You must include getGlobalNamesImpl if the class

file is P-coded.

classdef GlobalSysObjMatrix < matlab.System

methods (Access = protected)

function y = stepImpl(obj)

global B;

B(1,:) = B(1,:)+1;

y = B;

end

% Include getGlobalNamesImpl only if the class file is P-coded.

function globalNames = getGlobalNamesImpl(~)

globalNames = {"B"};

end

34 System object Usage and Authoring