@@ -0,0 +1,141 @@
4+{-# LANGUAGE DataKinds #-}
5+{-# LANGUAGE DeriveGeneric #-}
6+{-# LANGUAGE RankNTypes #-}
7+{-# LANGUAGE TypeOperators #-}
8+module Main (main, api, getLink, routesLinks, cliGet) where
10+import Control.Exception (throwIO)
11+import Control.Monad.Trans.Reader (ReaderT, runReaderT)
12+import Data.Proxy (Proxy (..))
13+import Network.Wai.Handler.Warp (run)
14+import System.Environment (getArgs)
19+import Servant.API.Generic
20+import Servant.Client.Generic
21+import Servant.Server.Generic
24+The usage is simple, if you only need a collection of routes.
25+First you define a record with field types prefixed by a parameter `route`:
28+data Routes route = Routes
29+ { _get :: route :- Capture "id" Int :> Get '[JSON] String
30+ , _put :: route :- ReqBody '[JSON] Int :> Put '[JSON] Bool
35+Then we'll use this data type to define API, links, server and client.
39+You can get a `Proxy` of the API using `genericApi`:
42+api :: Proxy (ToServantApi Routes)
43+api = genericApi (Proxy :: Proxy Routes)
46+It's recommended to use `genericApi` function, as then you'll get
47+better error message, for example if you forget to `derive Generic`.
51+The clear advantage of record-based generics approach, is that
52+we can get safe links very conveniently. We don't need to define endpoint types,
53+as field accessors work as proxies:
56+getLink :: Int -> Link
57+getLink = fieldLink _get
60+We can also get all links at once, as a record:
63+routesLinks :: Routes (AsLink Link)
64+routesLinks = allFieldLinks
69+Even more power starts to show when we generate a record of client functions.
70+Here we use `genericClientHoist` function, which lets us simultaneously
71+hoist the monad, in this case from `ClientM` to `IO`.
74+cliRoutes :: Routes (AsClientT IO)
75+cliRoutes = genericClientHoist
76+ (\x -> runClientM x env >>= either throwIO return)
78+ env = error "undefined environment"
80+cliGet :: Int -> IO String
81+cliGet = _get cliRoutes
86+Finally, probably the most handy usage: we can convert record of handlers into
87+the server implementation:
90+record :: Routes AsServer
92+ { _get = return . show
93+ , _put = return . odd
97+app = genericServe record
104+ putStrLn "Starting cookbook-generic at http://localhost:8000"
106+ -- see this cookbook below for custom-monad explanation
107+ ("run-custom-monad":_) -> do
108+ putStrLn "Starting cookbook-generic with a custom monad at http://localhost:8000"
109+ run 8000 (appMyMonad AppCustomState)
110+ _ -> putStrLn "To run, pass 'run' argument: cabal new-run cookbook-generic run"
113+## Using generics together with a custom monad
115+If your app uses a custom monad, here's how you can combine it with
119+data AppCustomState =
122+type AppM = ReaderT AppCustomState Handler
124+apiMyMonad :: Proxy (ToServantApi Routes)
125+apiMyMonad = genericApi (Proxy :: Proxy Routes)
127+getRouteMyMonad :: Int -> AppM String
128+getRouteMyMonad = return . show
130+putRouteMyMonad :: Int -> AppM Bool
131+putRouteMyMonad = return . odd
133+recordMyMonad :: Routes (AsServerT AppM)
134+recordMyMonad = Routes {_get = getRouteMyMonad, _put = putRouteMyMonad}
136+-- natural transformation
137+nt :: AppCustomState -> AppM a -> Handler a
138+nt s x = runReaderT x s
140+appMyMonad :: AppCustomState -> Application
141+appMyMonad state = genericServeT (nt state) recordMyMonad