Safe Haskell	Safe-Inferred
Language	Haskell2010

Data.GI.Base.DynVal

Description

This is an experimental module that introduces support for dynamic values: these are functions from a record model to some type a which keep track of which selectors of model does the result depend on. For example, for a record of the form

data Example = Example {
    first  :: Int,
    second :: Bool,
    third  :: Float
}

a `DynVal Example String` could be constructed, assuming that you are given a record DynVal representing the full record, using:

let format = \f s -> "First is " <> f <> " and second is " <> s
    formatted = format <$> record.first <*> record.second :: DynVal Example String

Here we are showcasing two properties of DynVals: they can be conveniently constructed using OverloadedRecordDot, and they provide an Applicative instance. The resulting formatted DynVal keeps track of the fact that it depends on the first and second record selectors.

Synopsis

data DynVal model a = DynVal DVKey (model -> a)
data DVKey
- = DVKeyDirect [Text]
- | DVKeyDerived (Set [Text])
data ModelProxy model = ModelProxy (IO model) (DVKey -> (model -> IO ()) -> IO ()) ([Text] -> (model -> Maybe model) -> IO ())
dvKeys :: DynVal model a -> DVKey
dvRead :: DynVal model a -> model -> a
modelProxyCurrentValue :: ModelProxy model -> IO model
modelProxyRegisterHandler :: ModelProxy model -> DVKey -> (model -> IO ()) -> IO ()
modelProxyUpdate :: ModelProxy model -> [Text] -> (model -> Maybe model) -> IO ()

Documentation

data DynVal model a Source #

A DynVal is a way of extracting values of type a from model, which keeps track of which fields (parameterised by dvKeys) in model are needed for computing the DynVal.

Constructors

DynVal DVKey (model -> a)

Instances

Instances details

(HasField fieldName field a, KnownSymbol fieldName) => HasField (fieldName :: Symbol) (DynVal model field) (DynVal model a) Source #
Instance details Defined in Data.GI.Base.DynVal Methods getField :: DynVal model field -> DynVal model a #
Applicative (DynVal model) Source #
Instance details Defined in Data.GI.Base.DynVal Methods pure :: a -> DynVal model a # (<>) :: DynVal model (a -> b) -> DynVal model a -> DynVal model b # liftA2 :: (a -> b -> c) -> DynVal model a -> DynVal model b -> DynVal model c # (>) :: DynVal model a -> DynVal model b -> DynVal model b # (<*) :: DynVal model a -> DynVal model b -> DynVal model a #
Functor (DynVal model) Source #
Instance details Defined in Data.GI.Base.DynVal Methods fmap :: (a -> b) -> DynVal model a -> DynVal model b # (<$) :: a -> DynVal model b -> DynVal model a #
IsString (DynVal model Text) Source #
Instance details Defined in Data.GI.Base.DynVal Methods fromString :: String -> DynVal model Text #

data DVKey Source #

Constructors

DVKeyDirect [Text]	Direct access to subfields: for example writing `record.field.subfield` (using the `HasField` instance) would lead to `DVKeyDirect ["field", "subfield"]`
DVKeyDerived (Set [Text])	Value derived from a direct key, by acting with the functor or applicative instances.

Instances

Instances details

Semigroup DVKey Source #	Joining of keys always produces derived ones.
Instance details Defined in Data.GI.Base.DynVal Methods (<>) :: DVKey -> DVKey -> DVKey # sconcat :: NonEmpty DVKey -> DVKey # stimes :: Integral b => b -> DVKey -> DVKey #
Show DVKey Source #
Instance details Defined in Data.GI.Base.DynVal Methods showsPrec :: Int -> DVKey -> ShowS # show :: DVKey -> String # showList :: [DVKey] -> ShowS #
Eq DVKey Source #
Instance details Defined in Data.GI.Base.DynVal Methods (==) :: DVKey -> DVKey -> Bool # (/=) :: DVKey -> DVKey -> Bool #
Ord DVKey Source #
Instance details Defined in Data.GI.Base.DynVal Methods compare :: DVKey -> DVKey -> Ordering # (<) :: DVKey -> DVKey -> Bool # (<=) :: DVKey -> DVKey -> Bool # (>) :: DVKey -> DVKey -> Bool # (>=) :: DVKey -> DVKey -> Bool # max :: DVKey -> DVKey -> DVKey # min :: DVKey -> DVKey -> DVKey #

data ModelProxy model Source #

A ModelProxy is a way of obtaining records of type model, which allows for registering for notifications whenever certain keys (typically associated to record fields) get modified, and allows to modify fields of the model.

Constructors

ModelProxy (IO model) (DVKey -> (model -> IO ()) -> IO ()) ([Text] -> (model -> Maybe model) -> IO ())

dvKeys :: DynVal model a -> DVKey Source #

Keys to fields in the model that this DynVal depends on.

dvRead :: DynVal model a -> model -> a Source #

Compute the actual value given a model.

modelProxyCurrentValue :: ModelProxy model -> IO model Source #

Obtain the current value of the model.

modelProxyRegisterHandler :: ModelProxy model -> DVKey -> (model -> IO ()) -> IO () Source #

Register a handler that will be executed whenever any of the fields in the model pointed to by the keys is modified.

modelProxyUpdate :: ModelProxy model -> [Text] -> (model -> Maybe model) -> IO () Source #

Modify the given keys in the proxy, using the given update function, of type (model -> Maybe model). If this function returns Nothing no modification will be performed, otherwise the modified model will be stored in the ModelProxy, and any listeners will be notified of a change.