levi.stephen wrote:
I have similar questions about Haskell abstracting away implementations behind interfaces as well. I have become used to an approach where I will not worry about databases/persistence when beginning. I will create an interface to a database layer (e.g., save(object), retrieve(id), findByName(name)) etc., and an implementation that uses in memory collections to begin with. Later I will replace this with database calls.
How does this type of approach work in Haskell? or what is the Haskell way to achieve this?
If OO is a good approach for a problem, it's straightforward to model it in haskell. If you plan to access an external DB in any case, then the interface will involve the IO Monad. Something along the lines of: data Object data ID data ObjectStore = ObjectStore { save :: Object -> IO ID, retrieve :: IO -> IO (Maybe Object), retrieveByName :: String -> IO (Maybe Object) } createMemoryStore :: IO ObjectStore connnectExternalStore :: ConnectionParams -> IO ObjectStore Tim