Haxl.Core.StateStore

Most users should import Haxl.Core instead of importing this module directly.

Documentation

class Typeable f => StateKey (f :: * -> *) where

StateKey maps one type to another type. A type that is an instance of StateKey can store and retrieve information from a StateStore.

Associated Types

data State f

Methods

getStateType :: Proxy f -> TypeRep

We default this to typeOf1, but if f is itself a complex type that is already applied to some paramaters, we want to be able to use the same state by using typeOf2, etc

Instances

Typeable * tag => StateKey (ConcurrentIOReq tag)

Associated Types

data State (ConcurrentIOReq tag :: * -> *) :: *

Methods

getStateType :: Proxy (* -> *) (ConcurrentIOReq tag) -> TypeRep

data StateStore

The StateStore maps a StateKey to the State for that type.

stateGet :: forall r. StateKey r => StateStore -> Maybe (State r)

Retrieves a State from the StateStore container.

stateSet :: forall f. StateKey f => State f -> StateStore -> StateStore

Inserts a State in the StateStore container.

stateEmpty :: StateStore

A StateStore with no entries.