Fristi
/ Aggregate.hs
Last active
November 6, 2022 20:50
DDD/Event Sourcing in Haskell. Implemented an aggregate as a type class and type families to couple event, command and error types specific to the aggregate. Errors are returned by using Either (Error e) (Event e). Applying Applicative Functors fits here well to sequentially check if the command suffice.
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| {-# LANGUAGE TypeFamilies #-} | |
| import Data.Function (on) | |
| import Control.Applicative | |
| data EventData e = EventData { | |
| eventId :: Int, | |
| body :: Event e | |
| } |