Matlab App - Value of numeric field to reset to default starting value if condition not met

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Hi folks,
I am creating an app in which I need to specify some numeric values, among which:
  • a start distance
  • an end distance
  • a step
This in turn creates a distance vector.
I then have 3 numeric fields that the user can edit with the desired distance.
I set a "default" starting value, which shows up in the boxes when the app starts.
I want to implement condition tests whenever the user tries to edit those fields. If the input start distance is higher than the end distance, it should display a warning message box and I would like the start distance to reset automatically to the value it was at. The problem is that the default starting value is stored as not stored as app.numericfield.DefaultValue but as app.numericfield.Value. So the default value is erased each time.
Has anyone got a solution for that?
Thanks in advance

Accepted Answer

Mario Malic
Mario Malic on 29 Apr 2021
Hi Antoine,
Assuming you have a simpler app, you can create a property that will hold your default values, for one or more components.
properties (Access = Public)
defValues = struct();
Then create a startupFcn callback (read about it), you can define initial values for some components from which you'll read default values
function startupFcn(app)
defValues.Component1 = 5;
defValues.Component2 = 2;
Then, in callback which changes the component value, you can set the default one in case condition is not fulfilled
function EditFieldValueChangedFcn(app, event)
if %condition
% do something
app.EditField.Value = app.defValues.Component1;
% uialert('title', 'text'); use uialert to display alerts/warnings
  1 Comment
Antoine Purier
Antoine Purier on 3 May 2021
Hi Mario,
Thaks for taking the time to provide such a complete answer.
It works perfectly after implementation.
I actually implemented something slightly different as I stored the previous value and not the default starting value. So the value that is in the text field just before entering a new "wrong" one.
But the logic is here!
Many thanks

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