Saving the values into a mat file error

Hy Guys. I hope you all are well. I have an urgent question as I am working on a big project. I am having an error in a code and I just want to fix this small error. I am saving the values into a mat file with my GUI and then uploading the values back by clicking on the save and upload button respectively.

However, I want my edit text boxes to write only letters and not alphabets. So, I entered an additional code where I make the letters read only and output Enter a number if an alphabet is written. However, my code shown above is not working for saving the values as it is giving me the errors:

cell contents reference from a non-cell array object.

Error in GUI_ParametersFinal>edit_TemperatureValue_Callback (line 187)

evalstring = sprintf('handles.mystructdata.%s.string = ''%s''',tagname,str{1});

This is my complete code:

function edit_TemperatureValue_Callback(hObject, eventdata, handles)

% hObject handle to edit_TemperatureValue (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of edit_TemperatureValue as text

% str2double(get(hObject,'String')) returns contents of edit_TemperatureValue as a double

str=get(hObject,'String');

tagname=get(hObject,'tag');

evalstring = sprintf('handles.mystructdata.%s.string = ''%s''',tagname,str{1});

evalc(evalstring);

guidata(hObject,handles)

For saving pushbutton, my code is

data = handles.mystructdata;

save('testmatfile.mat','data');

It will be so nice if someone can help :) Thank you so much.

Answer 1

[Stephen23]

Rather than this indirect, complex, buggy, obfuscated, strongly inadvisable code:

evalstring = sprintf('handles.mystructdata.%s.string = ''%s''',tagname,str{1});
evalc(evalstring);

just use simpler, neater, efficient, and much better dynamic fieldnames:

handles.mystructdata.(tagname).string = str{1};

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

"cell contents reference from a non-cell array object."

Clearly str is not a cell array, so your indexing will throw an error. It is worth noting that some GUI objects (e.g. some uicontrol types) can support the String property as either a character vector or cell array of character vectors: it is up to you to ensure/check this in the code. You might just need:

handles.mystructdata.(tagname).string = str;

or you could do something fancy like this:

if iscellstr(str)
    handles.mystructdata.(tagname).string = str{1};
else
    handles.mystructdata.(tagname).string = str;
end

[MHS]

Thank you so much for assistance. Yes, I got it. I will come back to you if I have any more problems :)