Safe Haskell	None
Language	Haskell2010

Hasura.SQL.BackendMap

Synopsis

newtype BackendMap (i :: BackendType -> Type) = BackendMap (Map BackendType (AnyBackend i))
singleton :: forall b i. HasTag b => i b -> BackendMap i
lookup :: forall (b :: BackendType) i. HasTag b => BackendMap i -> Maybe (i b)
elems :: forall i. BackendMap i -> [AnyBackend i]
modify :: forall b i. (HasTag b, Monoid (i b)) => (i b -> i b) -> BackendMap i -> BackendMap i
alter :: forall b i. HasTag b => (Maybe (i b) -> Maybe (i b)) -> BackendMap i -> BackendMap i

Documentation

newtype BackendMap (i :: BackendType -> Type) Source #

A BackendMap is a data structure that can contain at most one value of an i per BackendType The i type must be one that is parameterized by a BackendType-kinded type parameter

Constructors

BackendMap (Map BackendType (AnyBackend i))

Instances

Instances details

SatisfiesForAllBackends i Eq => Eq (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods (==) :: BackendMap i -> BackendMap i -> Bool # (/=) :: BackendMap i -> BackendMap i -> Bool #
SatisfiesForAllBackends i Show => Show (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods showsPrec :: Int -> BackendMap i -> ShowS # show :: BackendMap i -> String # showList :: [BackendMap i] -> ShowS #
Generic (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Associated Types type Rep (BackendMap i) :: Type -> Type # Methods from :: BackendMap i -> Rep (BackendMap i) x # to :: Rep (BackendMap i) x -> BackendMap i #
Semigroup (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods (<>) :: BackendMap i -> BackendMap i -> BackendMap i # sconcat :: NonEmpty (BackendMap i) -> BackendMap i # stimes :: Integral b => b -> BackendMap i -> BackendMap i #
Monoid (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods mempty :: BackendMap i # mappend :: BackendMap i -> BackendMap i -> BackendMap i # mconcat :: [BackendMap i] -> BackendMap i #
SatisfiesForAllBackends i FromJSON => FromJSON (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods parseJSON :: Value -> Parser (BackendMap i) parseJSONList :: Value -> Parser [BackendMap i]
SatisfiesForAllBackends i ToJSON => ToJSON (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap Methods toJSON :: BackendMap i -> Value toEncoding :: BackendMap i -> Encoding toJSONList :: [BackendMap i] -> Value toEncodingList :: [BackendMap i] -> Encoding
type Rep (BackendMap i) Source #
Instance details Defined in Hasura.SQL.BackendMap type Rep (BackendMap i) = D1 ('MetaData "BackendMap" "Hasura.SQL.BackendMap" "graphql-engine-1.0.0-inplace" 'True) (C1 ('MetaCons "BackendMap" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (Map BackendType (AnyBackend i)))))

singleton :: forall b i. HasTag b => i b -> BackendMap i Source #

lookup :: forall (b :: BackendType) i. HasTag b => BackendMap i -> Maybe (i b) Source #

Get a value from the map for the particular BackendType b. This function is usually used with a type application. lookup('Postgres 'Vanilla) backendMap @

elems :: forall i. BackendMap i -> [AnyBackend i] Source #

Get all values in the map

modify :: forall b i. (HasTag b, Monoid (i b)) => (i b -> i b) -> BackendMap i -> BackendMap i Source #

The expression modify f bmap alters the value x at b. modify is a restricted version of alter which cannot delete entries and if there is no b key present in the map, it will apply the modification function to the i b unit value and insert the result at b.

alter :: forall b i. HasTag b => (Maybe (i b) -> Maybe (i b)) -> BackendMap i -> BackendMap i Source #

The expression alter f bmap alters the value x at b, or absence thereof. alter can be used to insert, delete, or update a value in a Map.

In short : lookup k (alter f k m) = f (lookup k m).