Can anyone tell me why the function won't read the variables defined in the callback functions of this app?

So I'm coding a simple app:

        % Value changed function: DayDDEditField
        function DayDDEditFieldValueChanged(app, event)
            global DD
            value = app.DayDDEditField.Value;
            DD = value;
        end

        % Value changed function: MonthMMEditField
        function MonthMMEditFieldValueChanged(app, event)
            global MM
            value = app.MonthMMEditField.Value;
            MM = value;
        end

        % Value changed function: YearYYYYEditField
        function YearYYYYEditFieldValueChanged(app, event)
            global Y
            value = app.YearYYYYEditField.Value;
            Y = value;
        end

        % Value changed function: HourEditField
        function HourEditFieldValueChanged(app, event)
            global hour
            value = app.HourEditField.Value;
            hour = value;
        end

        % Value changed function: MinuteEditField
        function MinuteEditFieldValueChanged(app, event)
            global min
            value = app.MinuteEditField.Value;
            min = value;
        end

        % Value changed function: SecondEditField
        function SecondEditFieldValueChanged(app, event)
            global sec
            value = app.SecondEditField.Value;
            sec = value;
        end

        % Button pushed function: ConfirmButton
        function ConfirmButtonPushed(app, event)
            global DD MM Y
            opts = 'non-modal';
            year = num2str(Y);
            ycheck1 = floor(Y/4);
            ycheck2 = floor(Y/100);
            ycheck3 = floor(Y/400);
            if ((DD > 29) & (MM == 2))
                errordlg('February has 29 days max', 'Error!', opts);
                error('Error occurred!');
            end
            if ((ycheck2 == Y/100) & (ycheck3 ~= Y/400) & (DD == 29) & (MM == 2))
                errordlg(['Year ' year ' is not bissextile therefore February does not have 29 days'], 'Error!', opts);
                error('Error occurred!');
            end
            if ((DD == 29) & (MM == 2) & (ycheck1 ~= Y/4))
                errordlg(['Year ' year ' is not bissextile therefore February does not have 29 days'], 'Error!', opts);
                error('Error occurred!');
            else
                run('RightAscensionDate.m');
            end
        end
    end

(I've not copied the starting and ending lines that app designer writes by itself, the grey ones). As you can see at the end I run this function:

function [] = RightAscensionDate()
% Function to evaluate the right ascension of the Greenwich Meridian at the
% time selected by the user.
global DD MM Y JD hour min sec alphadate omegarot
omegarot = 2*pi/(23*60*60 + 56*60 + 4);
JD = juliandate(Y,MM,DD, hour, min, sec);           
T = (JD - 2415020)/36525;                          

alpha0 = (99.69083 + 36000.76892*T + 0.000387*T^2)*pi/180;
alphadate = alpha0 + omegarot*(hour*60*60 + min*60 + sec);
end

The problem is that the function doesn't seem to read the global variables (input arguments the user specifies in numeric fields in the UI figure) defined in the callback functions. I've checked and every time i push the "Confirm" button the function returns empty arrays of JD, T, alpha0 and alphadate, regardless of how I fill the numeric fields... Why does this happen?

[Adam]

Asking why anything happens with global variables is often a complicated question. why are you using global variables at all? Your app is a class. any functions of the class will have access to all variables you add as properties of the class instead of global variables and for external functions you should pass them as arguments. Your final function should just take those values in as arguments, then you wouldn't need to have to debug the mysteries of global variables. If you have access to your app when you call your function you have access to the properties too (if you make them public get access)

[Riccardo Basile]

I'm sorry if I keep asking you about this stuff, but it's the first time I code an app... How do I specify the app's properties? I don't know what you mean when you say to make them public neither. You mean I should use function handles?

[Adam]

At the top of your app file you will have a block something like this:

properties
   ...
 end
   

Those are your class properties. By default they will be greyed out and contain the various ui components.

You are free to add any more you want though in another block, e.g.

 properties( SetAccess = private, GetAccess = public )
    hour;
    min;
    sec;
 end  
    

You can then set these in a callback simply as

 app.hour = app.HourEditField.Value;

Even neater would be to use dependent properties, but that is more advanced so I won't suggest that!

[Riccardo Basile]

Well... You've pretty much opened my eyes! Thanks a lot, I owe you one!