MATLAB Not Assigning Variable

OK, so I have no idea what is going on here. I have been debugging a MATLAB UI I wrote with the help of GUIDE, and it appears MATLAB is simply refusing to assign a variable I tell it to. I have a variable called handles.connected_port, which is an empty serial port object (initially), as you can see below.

I also have a serial port that I created in scanning through all the available serial ports using seriallist I have named 'p'.

So far so good. However, when I execute the line of code

handles.connected_port = p;

absolutely nothing happens. In debug mode, in the line after that code is called, handles.connected_port is completely unchanged (see first figure) on the line immediately after execution. This feels like some serious non-determinism and I truly have no clue what's going on. MATLAB simply refuses to assign a variable to its proper value. This is perhaps the most bizarre error I've ever encountered. Is there something silly I'm missing?

Answer 1

[Walter Roberson]

Why would p be changed by assigning it to handles.connected_port ?

Note: if you are assigning to handles.connected_port inside a function, remember that only the local handles.connected_port would be affected. If you want to change the "master copy", you would need to use

guidata(hObject, handles)

to force it to update.

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

[Jordan Edmunds]

Sorry, meant to say handles.connected_port is unchanged. I call guidata(hObject, handles) a couple lines afterwards, but my concern is that handles.connected_port isn't even getting modified locally (the line immediately after execution). That's why it's so damn bizarre.

[Steven Lord]

Where is the handles structure that you have open in the Workspace browser located? Remember that handles is a struct array and as such uses value semantics. If you're inspecting the handles structure in the base workspace or some workspace other than the one in which you updated it, that will not change (even if you update the "master copy") until you explicitly "refresh" it using guidata.

It's like the handles structure is your credit card bill. Paying your bill will update the "master copy" in the credit card company's records, but it won't change the physical printed bill in your hand until you print out a new copy from your credit card company's website or they print out and send you an updated bill.