Calculations when values change

You will often want a calculation to update immediately whenever one of the attributes used by the calculations changes.

For example, if you have two numeric attributes on a window that are added together to give a third attribute, you will want the third attribute to update immediately if you change one of the other attributes:

if you change x or y, the x+y field updates immediately

To set up a calculation field that updates when you change its dependants:

1. In Object Designer, create the x, y, and x+y attributes.

Set the Default Value for x and y to 0, as described in Handling null values by setting a default value.

2. In the Properties grid for x+y, set the Calculation Type to BeforeSave.
   The Edit Formula dialog appears,
3. Enter the required formula, then click OK.
   for example:
   Value = Object._x + Object._y
   return Value
4. In Window Manager, add the three attributes to the required window.
5. For x and y, in the Window Manager Properties grid, set Is calculate on change to True.
6. Click .
   The window is saved. When you update x or y on the window, x+y immediately updates.

Is calculate on change has not been implemented in Workspaces, so you will not see this update until you reload the window.