How to use classes as Simulink lvl 2-M S-function custom-blocks?

I'm developing a Simulink model that has to access our library of Matlab classes. Although it should be, as of now, AFAIK, Simulink has no support for M-file S-functions that are classes instead of a bunch of functions. Anyway, I found a way to have an object available to the S-function and use it as a bridge. Details follow. The issue I am having is when calling methods in the object.

In the Simulink model I have a custom lvl 2-M S-funtion block configured as the code below shows. As you can see, in certain call-back functions I have lines that get a 'UserData' parameter from the runtime simulink block handle. Since 'UserData' can be anything I use it store an object. This is accomplished by adding

object_wrapper = someclass(param)
set_param(gcb,'UserData',object_wrapper)

in the InitFcn call-back in the Block properties dialog. The S-function is as follows (I only posted the setup and outputs function since the other registered call-backs are similar):

% Sfunction_wrapper
function Sfunction_wrapper(block)
setup(block);
end

function setup(block)
% Register number of ports
block.NumInputPorts  = 1;
block.NumOutputPorts = 2;
% Setup port properties to be inherited or dynamic
block.SetPreCompInpPortInfoToDynamic;
block.SetPreCompOutPortInfoToDynamic;
% Override input port properties
block.InputPort(1).DatatypeID  = 0;  % double
block.InputPort(1).Complexity  = 'Real';
block.InputPort(1).DirectFeedthrough = false;
% Override output port properties
block.OutputPort(1).DatatypeID  = 0; % double
block.OutputPort(1).Complexity  = 'Real';
block.OutputPort(2).DatatypeID  = 0; % double
block.OutputPort(2).Complexity  = 'Real';
block.SampleTimes = [1/20000 0];
block.RegBlockMethod('InitializeConditions', @InitializeConditions);
block.RegBlockMethod('Start', @Start);
block.RegBlockMethod('Outputs', @Outputs);
block.RegBlockMethod('Update', @Update);
block.RegBlockMethod('Terminate', @Terminate);
block.RegBlockMethod('SetInputPortSamplingMode', @SetInputPortSamplingMode);
end

function Outputs(block)
% Forward the call to the wrapper
wrapper_mainBlock = get_param(block.BlockHandle,'UserData');
wrapper_mainBlock.outputs(block);
end
% Similar functions for startup,etc,...

function SetInputPortSamplingMode(block,idx,fd)
block.InputPort(idx).SamplingMode = fd;
block.OutputPort(1).SamplingMode = fd;
block.OutputPort(2).SamplingMode = fd;    
end

The main point is in the Outputs function where I forward the calculation to the object wrapper. The idea is that inside the corresponding class I have easy access to all the library we have already developed and mainly to instantiated data (states) that can be of any type, contrary to DVectors wich can be only numerical. This would be a good enough solution except for the the following error I keep getting and I don't know why except that it could be something scope related??

Error while running output in someclass.m -> too many arguments... (stack trace)

The signature of the method is used correctly as you can see above. (This is not exactly the error message since I edited the code above.

Any ideas?

Kind regards,

Erwin

[Erwin Torreao Dassen]

I managed to get it running. Actually without any change. Apparently I had to restart Simulink (perhaps some class instances was being kept between runs?). But now, testing the setup with some data in the objects as states it seems I have hit a brick wall. In the outputs method of the somclass class I have the following:

function outputs(obj,block)
% Called to generate block outputs in simulation step.
obj.counter = obj.counter + 1;
block.OutputPort(2).Data = obj.counter;
block.OutputPort(1).Data = block.InputPort(1).Data;
end

which as shown should output (to the second port) the current counter (a property of instances of someclass.m) after iterating it. The thing is I get a constant output of 1 which is consistent with the scenario where Simulink at each simulation step instantiates a new object of someclass... The only way to have object properties as states is for this object to persist through the whole simulation. The help system is very limited in its wordings about the 'UserData' field. Is there anyway to obtain the persistence I need? Again, help is much appreciated.

Erwin

[Kaustubha Govind]

Is that the exact error that you see? It is an error about too many input arguments, or output arguments? Are you able to set a breakpoint at the line:

wrapper_mainBlock.outputs(block);

and step into someclass.m?

[Erwin Torreao Dassen]

The error about too many arguments was solved. Apparently it was related to changing the class file while the model had some hidden instances of the old version of the class (matlab doesn't see these variables).

I got this behaviour corrected for good by adding

delete(get_param(gcb,'UserData');

to the StopFcn callback.

With respect to the other problem (that of data/state persistence) I made someclass to be a handle class (subclassing the handle class), and now I got persistence!

So things appear to be solved!

Answer 1

[Erwin Torreao Dassen]

Solved in the comments above.

Main points:

1) someclass has to be a subclass of handle class so as to have data persistence.

2) Add a delete call to someclass in the StopFcn block callback function so as to really remove old instances from memory while developing. You get weird errors if you don't...