When you use the designer to determine what values to include in a drop-down field, you decide on the first value the user sees by selecting that value from the drop-down in the designer.
When the values of a drop-down field are determined using a formula, the drop-down in the designer is disabled. The reason is that the available values are not known until the app is run.
Instead, you need to set an initial value by assigning a formula to the InitialValue property. You do so by selecting InitialValue from the property drop-down in the inspector:
Example formulas
If you know that 2 is always part of the values the user can select from, simply use this formula:
If you don’t know what values will be available, and you want the first one to be selected initially, use this formula:
(The INDEX function above
selects the first value from the values of the
same drop-down field that the InitialValue property is associated
with, which is what Item references.)
If you want the last value to be selected initially, use this formula:
(SIZE returns the number of values of the drop-down field that the InitialValue property is associated with, which causes INDEX to return the last such value.)
Finally, to make the middle value selected, use this formula:
When is the InitialValue property consulted?
Traditionally, a field’s InitialValue property is only read when that field is about to be displayed. That typically happens when the user is about to navigate to the screen that contains it.
This used to apply to drop-down fields too. However, since drop-down field values can now change when the app is run, InitialValue is potentially read more often.
Consider a drop-down field for selecting a province. Another drop-down field determines the country, causing the drop-down field with provinces update accordingly.
What happens if a user selects a province and then changes the country? Since different countries rarely share province names, the selected province likely becomes invalid.
To handle this situation, the InitialValue property is now read in such cases. If it is associated with a formula, the formula is given the chance to determine which value is selected initially.