try and catch help

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In a callback function of a GUIDE gui, I have:
path = get(handles.path_text,'String')
try
data = importdata(path,'')
if istruct(data)
x_k = data.data;
else
x_k = data;
end
x_k_length = length(x_k);
catch err
error(end+1) = {'Error: Invalid input path.'};
fail_status = onfail(handles.check_path);
end
The idea here is if the input path is invalid, it will be caught and handeled so the callback function can continue. However, for some reason, when MATLAB executes the IF statement, it goes to the catch block. I don't understand why.

Accepted Answer

Leor Greenberger
Leor Greenberger on 3 Oct 2011
OOPS! should be two s's in isstruct.
getReport(err) in the catch block allowed me to solve it.

More Answers (2)

Walter Roberson
Walter Roberson on 3 Oct 2011
Please do not attempt to use error() as a variable name, especially considering the importance of error() to the try/catch mechanism!
I would tend to suspect that you do not want to use the empty string as the column delimiter.
Are you sure that path is non-empty and a regular string (not a cell array)? Should you not be checking with isempty() and ischar() ?
  1 Comment
Leor Greenberger
Leor Greenberger on 3 Oct 2011
oops. I actually was using error(k) here as a cell array of strings. Did not realize there is an error function as well.. will change the name.

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David Young
David Young on 3 Oct 2011
A better solution, and better practice in general, is for the code in the catch block to check the identifier of the error. If it can't handle it properly, it should rethrow the error, so it is reported correctly. In your case the catch block could check err.identifier to see that it was really thrown because of an invalid input path.
Also, since you are only expecting to deal with errors that come from importdata, it might be better to only have that statement in the try block:
try
data = importdata(...);
catch
...
end
if isstruct ...
  2 Comments
David Young
David Young on 3 Oct 2011
Yes, fair enough. I was thinking in terms of the catch block doing some error recovery or else making an early exit from the function.

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