GUI callbacks empty?

I inherited a GUI from an ex-colleague. It was made with GUIDE and has 30 or so items, including a lot of boxes to enter numbers. This is my first foray into GUI programming (in any language), and I thought I was getting the hang of it until I realized that many of the callbacks contain no code. Is it possible that there's some other magic code getting executed somewhere that I can't see?

[Ilya Gurin]

I think I figured out what's happening. It appears that entering data into the GUI object has no immediate effect. However, there's a button that reads the contents of a bunch of these objects and takes action accordingly. It seems slightly backwards to me, but maybe it's OK?

[Walter Roberson]

That is a common way of writing GUIs. For example if you have a GUI that needs you to enter latitude and longitude then it does not make much sense to have an action after entering only one of the two.

[Ilya Gurin]

Right. It's a similar situation here. All the numbers feed into one action. But if it were up to me, I would convert the entered text into numbers immediately and store it in a suitable structure. On the other hand, I can't think of a good reason why the way it's written would be wrong.

[Walter Roberson]

There is certainly merit to having GUIs do field validation upon entering information -- verifying that a numeric field is convertable to a number for example.

The newer App Designer numeric edit fields are inherently for numeric values, and so reduce the need for validation.