Error Handling in Simulink Using MSLException

Error Reporting in a Simulink Application

Simulink^® allows you to report an error by throwing an exception using the MSLException object, which is a subclass of the MATLAB^® MException class. As with the MATLAB MException object, you can use a try-catch block with a MSLException object construct to capture information about the error. The primary distinction between the MSLException and the MException objects is that the MSLException object has the additional property of handles. These handles allow you to identify the object associated with the error.

The MSLException Class

The MSLException class has five properties: identifier, message, stack, cause, and handles. The first four of these properties are identical to those of MException. For detailed information about them, see MException. The fifth property, handles, is a cell array with elements that are double array. These elements contain the handles to the Simulink objects (blocks or block diagrams) associated with the error.

Methods of the MSLException Class

The methods for the MSLException class are identical to those of the MException class. For details of these methods, see MException.

Capturing Information About the Error

The structure of the Simulink try-catch block for capturing an exception is:

try
		Perform one or more operations
catch E
		if isa(E, 'MSLException')
...
end

If an operation within the try statement causes an error, the catch statement catches the exception (E). Next, an if isa conditional statement tests to determine if the exception is Simulink specific, i.e., an MSLException. In other words, an MSLException is a type of MException.

The following code example shows how to get the handles associated with an error.

errHndls = [];
try
    sim('ModelName', ParamStruct);
catch e
    if isa(e,'MSLException')
			errHndls = e.handles{1}
    end
end

You can see the results by examining e. They will be similar to the following output:

e = 

  MSLException

  Properties:
       handles: {[7.0010]}
    identifier: 'Simulink:Parameters:BlkParamUndefined'
       message: [1x87 char]
         cause: {0x1 cell}
         stack: [0x1 struct]

  Methods, Superclasses

To identify the name of the block that threw the error, use the getfullname command. For the present example, enter the following command at the MATLAB command line:

getfullname(errHndls)

If a block named Mu threw an error from a model named vdp, MATLAB would respond to the getfullname command with:

ans =
vdp/Mu