Example of bags and kilograms
For example, there are 2 interdependent fields. The value in the second field should always be twice the value of the first field and vice versa.
We create the action code for changes in the first field:
=: set(table: $#ntn; field: 'field_2' = math`$#nfv * 2`; where: 'id' = #id)
We create the action code for changes in the second field:
=: set(table: $#ntn; field: 'field_1' = math`$#nfv / 2`; where: 'id' = #id)
What happens when the first field is changed — a new value will be set in the second field, triggering the change event there, and the action code will calculate the value for the first field and set it.
If no change occurs in the first field — the entire chain of codes will stop.
Be careful with such interdependent reciprocal action codes — if they do not reach equilibrium, the server will hang in an infinite loop until the timeout occurs.
The peculiarity of this calculation for the addition row?
In the addition row, there are no actions — therefore, this technique does not work in it. You can leave some key field editable, and calculate the others by code only during addition, blocking them specifically during addition.
In this case, you can move the addition to a temporary table and disable the addition row.