tutorial: make Client.lhs compile
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2 changed files with 22 additions and 12 deletions
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@ -15,12 +15,14 @@ need to have some language extensions and imports:
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module Client where
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import Control.Monad.Trans.Either
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import Control.Monad.Trans.Except
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import Data.Aeson
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import Data.Proxy
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import GHC.Generics
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import Network.HTTP.Client (Manager, newManager, defaultManagerSettings)
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import Servant.API
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import Servant.Client
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import System.IO.Unsafe
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```
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Also, we need examples for some domain specific data types:
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@ -70,13 +72,13 @@ What we are going to get with *servant-client* here is 3 functions, one to query
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``` haskell
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position :: Int -- ^ value for "x"
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-> Int -- ^ value for "y"
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-> EitherT ServantError IO Position
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-> ExceptT ServantError IO Position
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hello :: Maybe String -- ^ an optional value for "name"
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-> EitherT ServantError IO HelloMessage
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-> ExceptT ServantError IO HelloMessage
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marketing :: ClientInfo -- ^ value for the request body
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-> EitherT ServantError IO Email
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-> ExceptT ServantError IO Email
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```
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Each function makes available as an argument any value that the response may depend on, as evidenced in the API type. How do we get these functions? Just give a `Proxy` to your API and a host to make the requests to:
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@ -85,7 +87,12 @@ Each function makes available as an argument any value that the response may dep
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api :: Proxy API
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api = Proxy
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position :<|> hello :<|> marketing = client api (BaseUrl Http "localhost" 8081)
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{-# NOINLINE __manager #-}
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__manager :: Manager
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__manager = unsafePerformIO $ newManager defaultManagerSettings
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position :<|> hello :<|> marketing =
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client api (BaseUrl Http "localhost" 8081 "") __manager
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```
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As you can see in the code above, we just "pattern match our way" to these functions. If we try to derive less or more functions than there are endpoints in the API, we obviously get an error. The `BaseUrl` value there is just:
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@ -109,21 +116,21 @@ data BaseUrl = BaseUrl
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That's it. Let's now write some code that uses our client functions.
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``` haskell
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queries :: EitherT ServantError IO (Position, HelloMessage, Email)
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queries :: ExceptT ServantError IO (Position, HelloMessage, Email)
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queries = do
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pos <- position 10 10
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msg <- hello (Just "servant")
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message <- hello (Just "servant")
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em <- marketing (ClientInfo "Alp" "alp@foo.com" 26 ["haskell", "mathematics"])
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return (pos, msg, em)
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return (pos, message, em)
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run :: IO ()
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run = do
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res <- runEitherT queries
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res <- runExceptT queries
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case res of
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Left err -> putStrLn $ "Error: " ++ show err
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Right (pos, msg, em) -> do
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Right (pos, message, em) -> do
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print pos
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print msg
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print message
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print em
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```
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@ -15,7 +15,7 @@ cabal-version: >=1.10
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library
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exposed-modules: ApiType
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-- , Client
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, Client
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-- , Docs
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-- , Javascript
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-- , Server
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@ -45,6 +45,9 @@ library
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, http-types
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, transformers
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, markdown-unlit >= 0.4
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, http-client
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-- hs-source-dirs:
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default-language: Haskell2010
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ghc-options: -Wall -Werror -pgmL markdown-unlit
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-- to silence aeson-0.10 warnings:
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ghc-options: -fno-warn-missing-methods
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