Snap.Snaplet.AcidState

Documentation

newtype Acid st

Data type holding acid-state snaplet data.

Constructors

Acid

Fields

_acidStore :: AcidState st

Instances

HasAcid (Acid st) st

class HasAcid myState acidState | myState -> acidState where

Type class standardizing a context that holds an AcidState.

You can minimize boilerplate in your application by adding an instance like the following:

data App = App { ... _acid :: Snaplet (Acid MyState) ... }
instance HasAcid App MyState where
    getAcidStore = getL (snapletValue . acid)

Methods

getAcidStore :: myState -> Acid acidState

Instances

HasAcid (Acid st) st

acidInit

Arguments

:: (IsAcidic st, Typeable st)

=> st

Initial state to be used if

-> SnapletInit b (Acid st)

Initializer that stores the state in the "state/[typeOf state]/" directory.

acidInit'

Arguments

:: IsAcidic st

=> FilePath

Location of the acid-state store on disk

-> st

Initial state to be used if

-> SnapletInit b (Acid st)

Initializer allowing you to specify the location of the acid-state store.

acidInitMemory

Arguments

:: IsAcidic st

=> st

Initial state to be used if

-> SnapletInit b (Acid st)

Initializer allowing you to open an in-memory store (typically for testing)

acidInitManual

Arguments

:: IsAcidic st

=> AcidState st

AcidState state to be used

-> SnapletInit b (Acid st)

Initializer allowing you to specify the AcidState to use. This AcidState must be initialized manually elsewhere. It will not be automatically closed by the snaplet.

getAcidState :: (HasAcid s st, MonadSnaplet m, MonadState s (m b b)) => m b v (AcidState st)

Lower-level function providing direct access to the AcidState data type.

update :: (HasAcid s (MethodState event), MonadSnaplet m, MonadState s (m b b), UpdateEvent event, MonadIO (m b v)) => event -> m b v (EventResult event)

Wrapper for acid-state's update function that works for arbitrary instances of HasAcid.

query :: (HasAcid s (MethodState event), MonadSnaplet m, MonadState s (m b b), QueryEvent event, MonadIO (m b v)) => event -> m b v (EventResult event)

Wrapper for acid-state's query function that works for arbitrary instances of HasAcid.

createCheckpoint :: (MonadIO (m b v), MonadSnaplet m, MonadState s (m b b), HasAcid s st) => m b v ()

Wrapper for acid-state's createCheckpoint function that works for arbitrary instances of HasAcid.

createArchive :: (MonadIO (m b v), MonadSnaplet m, MonadState s (m b b), HasAcid s st) => m b v ()

Wrapper for acid-state's createArchive function that works for arbitrary instances of HasAcid.

closeAcidState :: (MonadIO (m b v), MonadSnaplet m, MonadState s (m b b), HasAcid s st) => m b v ()

Wrapper for acid-state's closeAcidState function that works for arbitrary instances of HasAcid. The state is automatically closed by the snaplet's unload action, but this is here in case the user needs more control.

initWorker :: IO (AcidState st) -> Initializer b v (Acid st)

Core init functionality common to both exported variants.

module Data.Acid