When applying events, for instance. In F#, you could do:
match msg with
| IncreaseCounter cnt ->
{ model with Count = model.Count + cnt }
| DecreaseCounter cnt ->
{ model with Count = model.Count - cnt }
| ResetCounter ->
{ model with Count = 0 }
| ChangeRubric name ->
{ model with Rubric = name, Count = 0 }
The "with" says: copy the original record by value, but change these fields. For completeness' sake: F# also has implicit returns, so the bit between brackets is the function's return value.
When applying events, for instance. In F#, you could do:
The "with" says: copy the original record by value, but change these fields. For completeness' sake: F# also has implicit returns, so the bit between brackets is the function's return value.
Python's dataclasses have a "make a copy with these fields changed" function that's rippingly useful for immutable records.