You can include System object™ code in Simulink® models using the MATLAB Function block. Your function can include one or more System objects. Portions of your system may be easier to implement in the MATLAB® environment than directly in Simulink. Many System objects have Simulink block counterparts with equivalent functionality. Before writing MATLAB code to include in a Simulink model, check for existing blocks that perform the desired operation.
You can include individual System objects that you create with a class definition file into Simulink using the MATLAB System block. This provides one way to add your own algorithm blocks into your Simulink models. For information, see System Object Integration in the Simulink documentation.