How to write a subfunction inside a GUI function?

I Would like to write a subfunction or subscript inside a GUI, but not a callback function, and I want to use any kind of global variables inside this function or subscript, or create new global variables in it. Is it possible?

Answer 1

[Walter Roberson]

Yes, it is possible.

In the case of App Designer you might have to define the function in a separate .m file if it is not a callback function and is not part of a constructor or method.

If you are using App Designer, it is not clear there is any point in using a global variable instead of a property of the class -- not unless, perhaps, you are working with multiple apps and wanting to communicate between them.

We recommend against using global variables in most cases; they are the slowest form of shared variable, and the more error-prone.

[Walter Roberson]

Please see http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F for information on better approaches than using global

[Merse Gaspar]

I first started looking this tutorial, which seemed official:

https://www.math.lsu.edu/system/files/BuildGUIs.pdf

Here, in the example script, the variables are global, and basically it's default, if I understand correctly. So a callback function doesn't need to pass what I've already initialized in the gui before.

If there's a way to do it, I'd like to do it in one file, but to avoid repetitions it would be nice to have some subroutines, e.g. reload_data(), replot(), etc., which can be activated by several callbacks.

[Walter Roberson]

When I search that document, I do not find any uses of global . Could you direct me to a specific page in the document that shows using global variables?

Are you looking at section 3, Create a Simple UI Programmatically ? If so then it does not use any global variables.

[Merse Gaspar]

I apologise if I did not use the term correctly. In that example, the whole GUI is in a single file (in a main function), and what is defined in the main body of that function is what I call global.

So, as far as I see, it is possible to use variables defined outside a subfunction (with a note about nested functions), but I cannot define new ones inside a subfunction.