Why is my custom System object not compatible with code generation?

I have a Simulink model that I created in R2022a and that contains a MATLAB System block that uses a custom System object. My System object has relatively simple methods and only a few properties (a public, tunable property, a public, variable-size, discrete state property, and a few other private properties).

When I run my model in "Interpreted execution" mode, my model simulates as expected. However, when I run my model in "Code generation" mode, I run into the following error stating that my System object is using code that does not support code generation.

 The error occurred for MATLAB System block 'MATLABSysObjCodeGenTest/MATLAB System'.    

 To prevent this error, use one of the following:
 * Modify the System object to avoid code that does not support code generation.
 * Change 'Simulate using' parameter to 'Interpreted Execution'.

 How can I make my System object code generation compatible?

Answer 1

[MathWorks Support Team]

In order for MATLAB System blocks to be code generation compatible, you cannot use variable-size for discrete state properties of System objects; however, private properties can be variable-size. The following link outlines this requirement along with others for specifically making System objects compatible with code generation:

https://www.mathworks.com/help/releases/R2022a/simulink/ug/use-system-objects-in-matlab-code-generation.html

Changing the public, variable-size, discrete state property to a private property instead should allow for the model to be code generation compatible.