Error Handling in Simulink Using MSLException Objects

Error Reporting in Simulink Applications

Simulink^® allows you to report an error by throwing an exception using the MSLException object, which is based on the MATLAB^® MException object. As with the MATLAB MException object, you can use a try-catch block with a MSLException object 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.

MSLException Objects

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.

MSLException Object Functions

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

Capturing Information About the Error

This code shows the structure of the try-catch block for capturing an MSLException. 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 an MSLException object, which indicates that the exception came from Simulink specific. In other words, an MSLException is a type of MException.

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

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

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

You can see the results by examining the variable e. The results look similar to this 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 function. For the present example, enter this command in the MATLAB Command Window.

getfullname(errHndls)

If a block named Mu threw an error from a model named vdp, the getfullname function returns the path to the block named Mu.

ans =
vdp/Mu