Documentation

Pipe operator

Returns the request path, e.g. /Users or /CreateUser

Returns the request path and the query params, e.g. /ShowUser?userId=9bd6b37b-2e53-40a4-bb7b-fdba67d6af42

Returns a header value for a given header name. Returns Nothing if not found

The header is looked up in a case insensitive way.

>>> getHeader "Content-Type"
Just "text/html"

>>> getHeader "X-My-Custom-Header"
Nothing

Returns the current HTTP request.

See https://hackage.haskell.org/package/wai-3.2.2.1/docs/Network-Wai.html#t:Request

A list of headers (a pair of key and value) in an HTTP request.

The WAI Request threaded through controllers and views as the ?context implicit parameter. All request-scoped state lives in request.vault (see RequestVault). The type alias is preserved for source compatibility with existing ?context :: ControllerContext type signatures.

Bind implicit parameters and run initContext for a controller action. Used by runActionWithNewContext and WebSocket handlers.

Sends a response to the client. Used by render functions.

This is the normal way to respond - it calls the WAI respond callback directly and returns the ResponseReceived.

Sends a response and exits the current action via early return. Sends the response via respondWith then throws EarlyReturnException so the action short-circuits.

Exit a request handler early after sending a response.

Use this when you want to conditionally exit a handler:

handler = do
    when someCondition do
        earlyReturn (sendErrorResponse ...)
    -- rest of the handler
    sendNormalResponse

The function runs the given IO action (which should send a response), then throws EarlyReturnException to exit. The middleware catches this exception so it doesn't propagate further.

Set a header value for a given header name.

>>> setHeader ("Content-Language", "en")

Returns a custom config parameter

>>> getAppConfig @StripePublicKey
StripePublicKey "pk_test_..."

Example:

First you need to define a custom config parameter in Config.hs:

-- Config/Config.hs
newtype StripePublicKey = StripePublicKey Text

config :: ConfigBuilder
config = do
    -- ...
    stripePublicKey <- StripePublicKey <$> env @Text "STRIPE_PUBLIC_KEY"
    option stripePublicKey

Then you can access it using getAppConfig:

action MyAction = do
    let (StripePublicKey stripePublicKey) = getAppConfig @StripePublicKey

    putStrLn ("Stripe public key: " <> stripePublicKey)

Type alias for WAI respond function

Information on the request sent by the client. This abstracts away the details of the underlying implementation.

Bind implicit parameters from a raw WAI request, insert the action type into the vault, and run initContext. Specialized once per application type. NOINLINE ensures GHC compiles one copy shared across all controllers.

Exceptions from initContext (including EarlyReturnException) propagate to the caller, which is expected to catch them.

A special datatype to indicate that the WAI handler has received the response. This is to avoid the need for Rank2Types in the definition of Application.

It is highly advised that only WAI handlers import and use the data constructor for this data type.

Since: wai-3.0.0