How to set a boolean property for one (and only one) list item ... be like a radio button selection
I would like to allow a model user to flag ONE member of a list as the "base item". If the user changes a leaf-level list item's "base item" flag to TRUE, then all other leaf-level list items that were previously marked TRUE should be marked FALSE. One and only one item must be "base item" = TRUE at any given time.
(Use case: Calculated line items will use this information to either compute values from inputs for all "base item" = FALSE items. For the one "base item" = TRUE item, the calculation applies different logic that "plugs" the remainder.)