Undefined variable in app designer when the variable called in external function

Below is the code in my first push button

 
[file,filepath,~]=uigetfile('*.xls*','Multiselect','on','Select Vos file');
app.filepath=fullfile(filepath,file);
app.filepathEditField.Value = app.filepath;

Below is the code in second push button where i am trying to call an external function when the second function is pushed

if(isempty(app.filepath))
    
    f = uifigure;
    uialert(f,'Please select all the files','Error');
    
else
  process_function;
end

the two codes above were wrote in appdesigner meanwhile the process function is an .m file

function a = process_function
[~,filename,fileext]=fileparts(app.filepath);
end

But i get the error in app designer showing undefined function of app.filepath. I really have no idea how to solve this, hope someone can give the the solution. Thanks in advance.

Answer 1

[Dennis]

Your external function does not know which variables you use in your app. You need to pass them along. Try changing

else
  process_function(app.filepath);
end

and

function a = process_function(filepath) 
[~,filename,fileext]=fileparts(filepath);
end

[Meng Li Gan]

Its work. Many thanks...