NgxExport.Tools.Combinators

Combinators of effectful actions

A set of convenient combinators of effectful actions for building handlers and services tuned for special purposes.

Void handler

voidHandler

Arguments

:: IO a

Target computation

-> IO ByteString

Runs an effectful computation and then returns an empty ByteString

This combinator saves printing the final return L.empty action in handlers that return unused or empty ByteString.

For example, handler signalUpconf being declared as an update callback in

type Upconf = [Text]

signalUpconf :: Upconf -> Bool -> IO L.ByteString
signalUpconf upconf = const $ do
    mapConcurrently_ getUrl upconf
    return L.empty

ngxExportSimpleServiceTyped 'signalUpconf ''Upconf $
    PersistentService Nothing

returns an empty bytestring which is not used in a meaningful way, therefore it can be rewritten as

signalUpconf :: Upconf -> Bool -> IO L.ByteString
signalUpconf = const . voidHandler . mapConcurrently_ getUrl

which helps to focus better on the computation itself.

Since: 1.2.0

Split services

module NgxExport.Tools.SplitService