Web.Scotty

It should be noted that most of the code snippets below depend on the OverloadedStrings language pragma.

scotty-to-WAI

scotty :: Port -> ScottyM () -> IO ()

Run a scotty application using the warp server.

scottyApp :: ScottyM () -> IO Application

Turn a scotty application into a WAI Application, which can be run with any WAI handler.

Defining Middleware and Routes

Middleware and routes are run in the order in which they are defined. All middleware is run first, followed by the first route that matches. If no route matches, a 404 response is given.

middleware :: Middleware -> ScottyM ()

Use given middleware. Middleware is nested such that the first declared is the outermost middleware (it has first dibs on the request and last action on the response). Every middleware is run on each request.

get :: Text -> ActionM () -> ScottyM ()

get = addroute GET

post :: Text -> ActionM () -> ScottyM ()

post = addroute POST

put :: Text -> ActionM () -> ScottyM ()

put = addroute PUT

delete :: Text -> ActionM () -> ScottyM ()

delete = addroute DELETE

addroute :: StdMethod -> Text -> ActionM () -> ScottyM ()

Define a route with a StdMethod, Text value representing the path spec, and a body (ActionM) which modifies the response.

 addroute GET "/" $ text "beam me up!"

The path spec can include values starting with a colon, which are interpreted as captures. These are named wildcards that can be looked up with param.

 addroute GET "/foo/:bar" $ do
     v <- param "bar"
     text v

>>> curl http://localhost:3000/foo/something
something

Defining Actions

Accessing the Request, Captures, and Query Parameters

request :: ActionM Request

Get the Request object.

param :: Text -> ActionM Text

Get a parameter. First looks in captures, then form data, then query parameters. Raises an exception which can be caught by rescue if parameter is not found.

Modifying the Response and Redirecting

status :: Status -> ActionM ()

Set the HTTP response status. Default is 200.

header :: Text -> Text -> ActionM ()

Set one of the response headers. Will override any previously set value for that header. Header names are case-insensitive.

redirect :: Text -> ActionM ()

Redirect to given URL. Like throwing an uncatchable exception. Any code after the call to redirect will not be run.

 redirect "http://www.google.com"

OR

 redirect "/foo/bar"

Setting Response

Note: only one of these should be present in any given route definition, as they completely replace the current Response body.

text :: Text -> ActionM ()

Set the body of the response to the given Text value. Also sets "Content-Type" header to "text/plain".

html :: Text -> ActionM ()

Set the body of the response to the given Text value. Also sets "Content-Type" header to "text/html".

file :: FilePath -> ActionM ()

Send a file as the response. Doesn't set the "Content-Type" header, so you probably want to do that on your own with header.

json :: ToJSON a => a -> ActionM ()

Set the body of the response to the JSON encoding of the given value. Also sets "Content-Type" header to "application/json".

Exceptions

raise :: Text -> ActionM a

Throw an exception, which can be caught with rescue. Uncaught exceptions turn into HTTP 500 responses.

rescue :: ActionM a -> (Text -> ActionM a) -> ActionM a

Catch an exception thrown by raise.

 raise "just kidding" `rescue` (\msg -> text msg)

Types

data ScottyM a

Instances

Monad ScottyM

Functor ScottyM

MonadIO ScottyM

MonadState ScottyState ScottyM

data ActionM a

Instances

Monad ActionM

Functor ActionM

MonadIO ActionM

MonadError ActionError ActionM

MonadState Response ActionM

MonadReader (Request, [Param]) ActionM