Reading in and Evaluating strings from standalone GUI using appdata

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Matthew
Matthew 2012-10-30
I have been attempting to write a standalone windows GUI for a program that I have. It necessitates that I allow the user to input a string function for a number of items and at some point in the code it executes said strings. The final value of the strings are a function of an array (T) and output an array [item name](j). There is already a string value stored in appdata with the same name (a default in case no user changes are made).
For example.
Default written into program:
setappdata(0,'Item1' , '50.^(-7590/T(j)-7.46)');
In user window, a box with a custom entry such as:
50.^(-150/T(j)+1) and a corresponding GUI code for
setappdata(0,'Item1',get(handles.edit107,'string'));
where the tag of the text box is edit107
and a subsequent evaluation of
Item1result(j)=eval(getappdata(0,'Item1'));
Assuming the T and j are both defined properly as arrays.
In the certain situation where a user might enter just a single number (which is realistic).
Is there anyway around the:
Undefined function 'eval' for input arguments of type 'double'.

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回答（2 个）

Robert Cumming
Robert Cumming 2012-10-30
Am I correct in assuming the user enters any string which then gets executed in eval? This is NOT advisable.... for example: the user could enter: 'system ( 'delete C:\*' )'
Anyway - to answer your questions: have you seen
try
do something
catch % if it errors - the error is captured
do something else
end
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Matthew
Matthew 2012-10-30
Wow I hadn't considered that to be a possibility, yikes, thanks for the heads up. While I'm fairly confident that would never be the case, is there a safer evaluation method?
I also hadn't previously been aware of the try function, thank you!

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Matthew
Matthew 2012-10-30
On this same note, is there any simpler way to check if the input is a number and if it isn't assume that it is a string and evaluate?
Ex:
if isnumeric(getappdata(0,'Item1'))
Item1R=getappdata(0,'Item1');
else
Item1R=eval(getappdata(0,'Item1'));
end
If there is no way for the eval function to process a number by itself (or an alternative function) then i need to do the above for about 150 some items...
  1 个评论
Robert Cumming
Robert Cumming 2012-11-1
You should add this to your original question - since it builds on your question - but yes isnumeric is a satisfactory way of checking if a variable is a number.
Perhaps if you expalin your aim in more detail you might get more help on avoiding eval.
Have you seen this link on avoiding eval?

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