What are the differences (if any) between Matlab system objects and class objects?

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Matlab includes a wide variety of System Objects, that seem to be standard Matlab objects (typically singletons) which derive from matlab.System ( ref ).
My question: is there any real difference between System Objects and any other class object used in Matlab?

Accepted Answer

Kaustubha Govind
Kaustubha Govind on 10 Jan 2013
Edited: Kaustubha Govind on 10 Jan 2013
In my own words, System objects are a subset of standard MATLAB class objects which inherit from an interface class named matlab.System. The interface class specifies methods that should be implemented by an author of a System object - each of these methods determine the behavior of the System object (eg. getNumInputsImpl, getNumOutputsImpl, stepImpl, etc.). In essence, System objects provide an infrastructure/platform for you to define a "system" in MATLAB.
I think the concept of System objects will more completely resonate with Simulink users, because IMHO System objects are a lot like S-functions, except that they can be used the same way in both MATLAB and Simulink. Methods like setupImpl, resetImpl, stepImpl, releaseImpl, etc. can be used to define a system more completely, as opposed to a MATLAB function which can only define an algorithm, but not a system.
Tong Zhao
Tong Zhao on 27 Jul 2021
Edited: Tong Zhao on 27 Jul 2021
Good explanation. So the way I see, matlab system objects are implementations of an interface class that characterizes a stepped (assuming that you're utilizing the stepImpl method to step the system states) multiple input multipl output (MIMO) dynamical system (dynamical because it stores states, or rather properties in class language).

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More Answers (2)

Arnav Mendiratta
Arnav Mendiratta on 24 Jul 2017
Here is a good blog post about system objects: https://blogs.mathworks.com/simulink/2013/09/11/the-matlab-system-block/
This post is from 2013 and since then, the syntax for some functions (like step does not require a call like step(obj) anymore) might have changed.

Sean de Wolski
Sean de Wolski on 10 Jan 2013
There are a few things that come with system objects. Most importantly: codegen support. Also, large data stream processing, saved state information and fixed-point support.
Kaustubha Govind
Kaustubha Govind on 10 Jan 2013
Yair: I think the primary difference would be that all System objects have a standard interface, and the System object infrastructure automatically provides consistency checking, and possibly other services (can't think of more examples right now), that are shared by all System objects.

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