Thread Subject: GUI, evaluate 'return' in caller

Hi,

I am working on a GUI. For it, I wrote a subroutine (stored
in a different .m file from the GUI) that checks the user's
answers to various dialog boxes such as listdlg or inputdlg
to see that the answers are valid before continuing. In the
case of an invalid answer the code should just evaluate the
command 'return' and not continue on with the bad answer.

Most of the code works as planned but I can't get the error
checking subroutine to actually evaluate the command
'return' in the calling function. I was trying to do this
by using the following code in the error checker, but it
doesn't seem to work. Any ideas what I am doing wrong?

if valid_answer==0
   msgbox('invalid answer')
   cmd = 'return';
   evalin('caller',cmd);
end


An alternative I considered was to have the error checker
return a variable indicating whether there is an error, and
then using an if statement within the GUI function as shown
below. This would also get the job done, but I hoped to not
have to repeat this code 20 times in my program for all the
places where there are user inputs.

valid_answer = errorchecker(answer,valid_answers);
if valid_answer==0
   msgbox('invalid answer')
   return
end

In case it makes a difference, I am using version 7.1.0.246.

Thanks,
J

"jay vaughan" <jvaughan5.nospam@gmail.com> wrote in message
<fu86o0$phi$1@fred.mathworks.com>...
> Hi,
>
> I am working on a GUI. For it, I wrote a subroutine
(stored
> in a different .m file from the GUI) that checks the
user's
> answers to various dialog boxes such as listdlg or
inputdlg
> to see that the answers are valid before continuing. In
the
> case of an invalid answer the code should just evaluate
the
> command 'return' and not continue on with the bad answer.
>
> Most of the code works as planned but I can't get the
error
> checking subroutine to actually evaluate the command
> 'return' in the calling function. I was trying to do this
> by using the following code in the error checker, but it
> doesn't seem to work. Any ideas what I am doing wrong?
>
> if valid_answer==0
> msgbox('invalid answer')
> cmd = 'return';
> evalin('caller',cmd);
> end
>
>
> An alternative I considered was to have the error checker
> return a variable indicating whether there is an error,
and
> then using an if statement within the GUI function as
shown
> below. This would also get the job done, but I hoped to
not
> have to repeat this code 20 times in my program for all
the
> places where there are user inputs.
>
> valid_answer = errorchecker(answer,valid_answers);
> if valid_answer==0
> msgbox('invalid answer')
> return
> end
>
> In case it makes a difference, I am using version
7.1.0.246.
>
> Thanks,
> J
>
>

Note that even "eval('return')" doesn't work. I suggest
your second option is by far the better method (eval is
evil). You can simplify it to:

if errorchecker(answer,valid_answers)
  return
end

and have ERRORCHECKER display the msgbox and return a
logical.