Understanding Expression Nuances. - I want to...

expressions
(Grant Stead) #1

Understanding Expression Nuances. - I want to make sure I’ve got this right.

A Virtual Column recalculates when?

  • An app formula only recalculates when a record is opened/initially created. i.e. you have to touch it in order for it to calculate. If I have a PO with a total amount, and PO lines with costs. If I go in the back end, and adjust a single line items cost, the app will NEVER recalculate the PO total if the PO record is never actually opened in the app?

  • I can use an expression in the initial box, but then it’s order based, if the user changes something, and then goes back up, it’s not live, like once it pops, it’s done.

  • A Sheet formula isn’t live until you get a good sync. Will the sync ALWAYS pick up the results or are there cases where it doesn’t catch the results of the formulas?

  • Is there a way to have an app formula that calculates live throughout filling in a form, and then locks down once it’s submitted and won’t change upon subsequent reopens?

(Praveen Seshadri (AppSheet)) #2
  1. yes app formulas are meant for computations in the app. If you directly change something in the backend, AppSheet isn’t aware of it.

  2. initial value expressions are only relevant when creating a new row. they will repeatedly be evaluated (as other columns are filled in) until the row is saved or the value is overwritten explicitly by the user

  3. a sheet formula is meant for backend calculations. AppSheet doesn’t run these formulas. columns with sheet formulas are read-only from AppSheet’s POV

  4. you can write an AppFormula like this: IF([ISBLANK([_THIS], , [_THIS])

— so it will calculate initially until non-blank and then won’t.

(Grant Stead) #3

Thanks for #4, that’s a huge help