Yesod.Core

Type classes

class RenderRoute site => Yesod site where

Define settings for a Yesod applications. All methods have intelligent defaults, and therefore no implementation is required.

Minimal complete definition

Nothing

Methods

approot :: Approot site

An absolute URL to the root of the application. Do not include trailing slash.

Default value: ApprootRelative. This is valid under the following conditions:

• Your application is served from the root of the domain.
• You do not use any features that require absolute URLs, such as Atom feeds and XML sitemaps.

If this is not true, you should override with a different implementation.

errorHandler :: ErrorResponse -> HandlerT site IO TypedContent

Output error response pages.

Default value: defaultErrorHandler.

defaultLayout :: WidgetT site IO () -> HandlerT site IO Html

Applies some form of layout to the contents of a page.

urlRenderOverride :: site -> Route site -> Maybe Builder

Override the rendering function for a particular URL. One use case for this is to offload static hosting to a different domain name to avoid sending cookies.

isAuthorized

Arguments

:: Route site

-> Bool

is this a write request?

-> HandlerT site IO AuthResult

Determine if a request is authorized or not.

Return Authorized if the request is authorized, Unauthorized a message if unauthorized. If authentication is required, return AuthenticationRequired.

isWriteRequest :: Route site -> HandlerT site IO Bool

Determines whether the current request is a write request. By default, this assumes you are following RESTful principles, and determines this from request method. In particular, all except the following request methods are considered write: GET HEAD OPTIONS TRACE.

This function is used to determine if a request is authorized; see isAuthorized.

authRoute :: site -> Maybe (Route site)

The default route for authentication.

Used in particular by isAuthorized, but library users can do whatever they want with it.

cleanPath :: site -> [Text] -> Either [Text] [Text]

A function used to clean up path segments. It returns Right with a clean path or Left with a new set of pieces the user should be redirected to. The default implementation enforces:

• No double slashes
• There is no trailing slash.

Note that versions of Yesod prior to 0.7 used a different set of rules involing trailing slashes.

joinPath

Arguments

:: site

-> Text

application root

-> [Text]

path pieces

-> [(Text, Text)]

query string

-> Builder

Builds an absolute URL by concatenating the application root with the pieces of a path and a query string, if any. Note that the pieces of the path have been previously cleaned up by cleanPath.

addStaticContent

Arguments

:: Text

filename extension

-> Text

mime-type

-> ByteString

content

-> HandlerT site IO (Maybe (Either Text (Route site, [(Text, Text)])))

This function is used to store some static content to be served as an external file. The most common case of this is stashing CSS and JavaScript content in an external file; the Yesod.Widget module uses this feature.

The return value is Nothing if no storing was performed; this is the default implementation. A Just Left gives the absolute URL of the file, whereas a Just Right gives the type-safe URL. The former is necessary when you are serving the content outside the context of a Yesod application, such as via memcached.

maximumContentLength :: site -> Maybe (Route site) -> Maybe Word64

Maximum allowed length of the request body, in bytes.

If Nothing, no maximum is applied.

Default: 2 megabytes.

makeLogger :: site -> IO Logger

Creates a Logger to use for log messages.

Note that a common technique (endorsed by the scaffolding) is to create a Logger value and place it in your foundation datatype, and have this method return that already created value. That way, you can use that same Logger for printing messages during app initialization.

Default: the defaultMakeLogger function.

messageLoggerSource

Arguments

:: site

-> Logger

-> Loc

position in source code

-> LogSource

-> LogLevel

-> LogStr

message

-> IO ()

Send a message to the Logger provided by getLogger.

Default: the defaultMessageLoggerSource function, using shouldLogIO to check whether we should log.

jsLoader :: site -> ScriptLoadPosition site

Where to Load sripts from. We recommend the default value, BottomOfBody. Alternatively use the built in async yepnope loader:

BottomOfHeadAsync $ loadJsYepnope $ Right $ StaticR js_modernizr_js

Or write your own async js loader.

makeSessionBackend :: site -> IO (Maybe SessionBackend)

Create a session backend. Returning Nothing disables sessions. If you'd like to change the way that the session cookies are created, take a look at customizeSessionCookies.

Default: Uses clientsession with a 2 hour timeout.

fileUpload :: site -> RequestBodyLength -> FileUpload

How to store uploaded files.

Default: When the request body is greater than 50kb, store in a temp file. For chunked request bodies, store in a temp file. Otherwise, store in memory.

shouldLog :: site -> LogSource -> LogLevel -> Bool

Should we log the given log source/level combination.

Default: the defaultShouldLog function.

shouldLogIO :: site -> LogSource -> LogLevel -> IO Bool

Should we log the given log source/level combination.

Note that this is almost identical to shouldLog, except the result lives in IO. This allows you to dynamically alter the logging level of your application by having this result depend on, e.g., an IORef.

The default implementation simply uses shouldLog. Future versions of Yesod will remove shouldLog and use this method exclusively.

Since 1.2.4

yesodMiddleware :: ToTypedContent res => HandlerT site IO res -> HandlerT site IO res

A Yesod middleware, which will wrap every handler function. This allows you to run code before and after a normal handler.

Default: the defaultYesodMiddleware function.

Since: 1.1.6

yesodWithInternalState :: site -> Maybe (Route site) -> (InternalState -> IO a) -> IO a

How to allocate an InternalState for each request.

The default implementation is almost always what you want. However, if you know that you are never taking advantage of the MonadResource instance in your handler functions, setting this to a dummy implementation can provide a small optimization. Only do this if you really know what you're doing, otherwise you can turn safe code into a runtime error!

Since 1.4.2

Instances

Yesod LiteApp

class Yesod site => YesodDispatch site where

This class is automatically instantiated when you use the template haskell mkYesod function. You should never need to deal with it directly.

Methods

yesodDispatch :: YesodRunnerEnv site -> Application

Instances

YesodDispatch LiteApp

class YesodSubDispatch sub m where

Methods

yesodSubDispatch :: YesodSubRunnerEnv sub (HandlerSite m) m -> Application

Instances

YesodSubDispatch WaiSubsite master

class Eq (Route a) => RenderRoute a where

Associated Types

data Route a

The type-safe URLs associated with a site argument.

Methods

renderRoute

Arguments

:: Route a

-> ([Text], [(Text, Text)])

The path of the URL split on forward slashes, and a list of query parameters with their associated value.

Instances

RenderRoute WaiSubsite

RenderRoute LiteApp

class RenderRoute a => ParseRoute a where

Methods

parseRoute

Arguments

:: ([Text], [(Text, Text)])

The path of the URL split on forward slashes, and a list of query parameters with their associated value.

-> Maybe (Route a)

Instances

ParseRoute WaiSubsite

ParseRoute LiteApp

class RenderRoute a => RouteAttrs a where

Methods

routeAttrs

Arguments

:: Route a

-> Set Text

A set of attributes associated with the route.

Breadcrumbs

class YesodBreadcrumbs site where

A type-safe, concise method of creating breadcrumbs for pages. For each resource, you declare the title of the page and the parent resource (if present).

Methods

breadcrumb :: Route site -> HandlerT site IO (Text, Maybe (Route site))

Returns the title and the parent resource, if available. If you return a Nothing, then this is considered a top-level page.

breadcrumbs :: YesodBreadcrumbs site => HandlerT site IO (Text, [(Route site, Text)])

Gets the title of the current page and the hierarchy of parent pages, along with their respective titles.

Types

data Approot master

How to determine the root of the application for constructing URLs.

Note that future versions of Yesod may add new constructors without bumping the major version number. As a result, you should not pattern match on Approot values.

Constructors

ApprootRelative

No application root.

ApprootStatic !Text

ApprootMaster !(master -> Text)

ApprootRequest !(master -> Request -> Text)

data FileUpload

Constructors

FileUploadMemory !(BackEnd ByteString)

FileUploadDisk !(InternalState -> BackEnd FilePath)

FileUploadSource !(BackEnd (Source (ResourceT IO) ByteString))

data ErrorResponse

Responses to indicate some form of an error occurred.

Constructors

NotFound

InternalError Text

InvalidArgs [Text]

NotAuthenticated

PermissionDenied Text

BadMethod Method

Instances

Eq ErrorResponse

Show ErrorResponse

Utitlities

maybeAuthorized

Arguments

:: Yesod site

=> Route site

-> Bool

is this a write request?

-> HandlerT site IO (Maybe (Route site))

Return the same URL if the user is authorized to see it.

Built on top of isAuthorized. This is useful for building page that only contain links to pages the user is allowed to see.

widgetToPageContent :: (Eq (Route site), Yesod site) => WidgetT site IO () -> HandlerT site IO (PageContent (Route site))

Convert a widget to a PageContent.

Defaults

defaultErrorHandler :: Yesod site => ErrorResponse -> HandlerT site IO TypedContent

The default error handler for errorHandler.

defaultYesodMiddleware :: Yesod site => HandlerT site IO res -> HandlerT site IO res

Default implementation of yesodMiddleware. Adds the response header "Vary: Accept, Accept-Language" and performs authorization checks.

Since 1.2.0

authorizationCheck :: Yesod site => HandlerT site IO ()

Check if a given request is authorized via isAuthorized and isWriteRequest.

Since 1.2.0

Data types

data AuthResult

Constructors

Authorized

AuthenticationRequired

Unauthorized Text

Instances

Eq AuthResult

Read AuthResult

Show AuthResult

unauthorizedI :: (MonadHandler m, RenderMessage (HandlerSite m) msg) => msg -> m AuthResult

Return an Unauthorized value, with the given i18n message.

Logging

defaultMakeLogger :: IO Logger

Default implementation of makeLogger. Sends to stdout and automatically flushes on each write.

Since 1.4.10

defaultMessageLoggerSource

Arguments

:: (LogSource -> LogLevel -> IO Bool)

Check whether we should log this

-> Logger

-> Loc

position in source code

-> LogSource

-> LogLevel

-> LogStr

message

-> IO ()

Default implementation of messageLoggerSource. Checks if the message should be logged using the provided function, and if so, formats using formatLogMessage. You can use defaultShouldLogIO as the provided function.

Since 1.4.10

defaultShouldLog :: LogSource -> LogLevel -> Bool

Default implementation of shouldLog. Logs everything at or above LevelInfo.

Since 1.4.10

defaultShouldLogIO :: LogSource -> LogLevel -> IO Bool

A default implementation of shouldLogIO that can be used with defaultMessageLoggerSource. Just uses defaultShouldLog.

Since 1.4.10

formatLogMessage

Arguments

:: IO ZonedDate

-> Loc

-> LogSource

-> LogLevel

-> LogStr

message

-> IO LogStr

Default formatting for log messages. When you use the template haskell logging functions for to log with information about the source location, that information will be appended to the end of the log. When you use the non-TH logging functions, like logDebugN, this function does not include source information. This currently works by checking to see if the package name is the string "<unknown>". This is a hack, but it removes some of the visual clutter from non-TH logs.

Since 1.4.10

data LogLevel :: *

Constructors

LevelDebug

LevelInfo

LevelWarn

LevelError

LevelOther Text

Instances

Eq LogLevel

Ord LogLevel

Read LogLevel

Show LogLevel

Lift LogLevel

logDebug :: Q Exp

Generates a function that takes a Text and logs a LevelDebug message. Usage:

$(logDebug) "This is a debug log message"

logInfo :: Q Exp

See logDebug

logWarn :: Q Exp

See logDebug

logError :: Q Exp

See logDebug

logOther :: Text -> Q Exp

Generates a function that takes a Text and logs a LevelOther message. Usage:

$(logOther "My new level") "This is a log message"

logDebugS :: Q Exp

Generates a function that takes a LogSource and Text and logs a LevelDebug message. Usage:

$logDebugS "SomeSource" "This is a debug log message"

logInfoS :: Q Exp

See logDebugS

logWarnS :: Q Exp

See logDebugS

logErrorS :: Q Exp

See logDebugS

logOtherS :: Q Exp

Generates a function that takes a LogSource, a level name and a Text and logs a LevelOther message. Usage:

$logOtherS "SomeSource" "My new level" "This is a log message"

Sessions

newtype SessionBackend

Constructors

SessionBackend

Fields

sbLoadSession :: Request -> IO (SessionMap, SaveSession)

Return the session data and a function to save the session

customizeSessionCookies :: (SetCookie -> SetCookie) -> SessionBackend -> SessionBackend

Customize the cookies used by the session backend. You may use this function on your definition of makeSessionBackend.

For example, you could set the cookie domain so that it would work across many subdomains:

makeSessionBackend site =
    (fmap . fmap) (customizeSessionCookies addDomain) ...
  where
    addDomain cookie = cookie { setCookieDomain = Just ".example.com" }

Default: Do not customize anything (id).

defaultClientSessionBackend

Arguments

:: Int

minutes

-> FilePath

key file

-> IO SessionBackend

envClientSessionBackend

Arguments

:: Int

minutes

-> String

environment variable name

-> IO SessionBackend

Create a SessionBackend which reads the session key from the named environment variable.

This can be useful if:

1. You can't rely on a persistent file system (e.g. Heroku)
2. Your application is open source (e.g. you can't commit the key)

By keeping a consistent value in the environment variable, your users will have consistent sessions without relying on the file system.

Note: A suitable value should only be obtained in one of two ways:

1. Run this code without the variable set, a value will be generated and printed on devstdout/
2. Use clientsession-generate

Since 1.4.5

clientSessionBackend

Arguments

:: Key

The encryption key

-> IO ClientSessionDateCache

See clientSessionDateCacher

-> SessionBackend

sslOnlySessions :: IO (Maybe SessionBackend) -> IO (Maybe SessionBackend)

Defends against session hijacking by setting the secure bit on session cookies so that browsers will not transmit them over http. With this setting on, it follows that the server will regard requests made over http as sessionless, because the session cookie will not be included in the request. Use this as part of a total security measure which also includes disabling HTTP traffic to the site or issuing redirects from HTTP urls, and composing sslOnlyMiddleware with the site's yesodMiddleware.

Since 1.4.7

sslOnlyMiddleware

Arguments

:: Yesod site

=> Int

minutes

-> HandlerT site IO res

-> HandlerT site IO res

Apply a Strict-Transport-Security header with the specified timeout to all responses so that browsers will rewrite all http links to https until the timeout expires. For security, the max-age of the STS header should always equal or exceed the client sessions timeout. This defends against hijacking attacks on the sessions of users who attempt to access the site using an http url. This middleware makes a site functionally inaccessible over vanilla http in all standard browsers.

Since 1.4.7

clientSessionDateCacher

Arguments

:: NominalDiffTime

Inactive session valitity.

-> IO (IO ClientSessionDateCache, IO ())

loadClientSession

Arguments

:: Key

-> IO ClientSessionDateCache

See clientSessionDateCacher

-> ByteString

session name

-> Request

-> IO (SessionMap, SaveSession)

data Header

Headers to be added to a Result.

Constructors

AddCookie SetCookie

DeleteCookie ByteString ByteString

Header ByteString ByteString

Instances

Eq Header

Show Header

NFData Header

CSRF protection

defaultCsrfMiddleware :: Yesod site => HandlerT site IO res -> HandlerT site IO res

Calls defaultCsrfSetCookieMiddleware and defaultCsrfCheckMiddleware.

For details, see the "AJAX CSRF protection" section of Yesod.Core.Handler.

Since 1.4.14

defaultCsrfSetCookieMiddleware :: Yesod site => HandlerT site IO res -> HandlerT site IO res

Calls csrfSetCookieMiddleware with the defaultCsrfCookieName.

Since 1.4.14

csrfSetCookieMiddleware :: Yesod site => HandlerT site IO res -> SetCookie -> HandlerT site IO res

Takes a SetCookie and overrides its value with a CSRF token, then sets the cookie. See setCsrfCookieWithCookie.

For details, see the "AJAX CSRF protection" section of Yesod.Core.Handler.

Since 1.4.14

defaultCsrfCheckMiddleware :: Yesod site => HandlerT site IO res -> HandlerT site IO res

Calls csrfCheckMiddleware with isWriteRequest, defaultCsrfHeaderName, and defaultCsrfParamName as parameters.

Since 1.4.14

csrfCheckMiddleware

Arguments

:: Yesod site

=> HandlerT site IO res

-> HandlerT site IO Bool

Whether or not to perform the CSRF check.

-> CI ByteString

The header name to lookup the CSRF token from.

-> Text

The POST parameter name to lookup the CSRF token from.

-> HandlerT site IO res

Looks up the CSRF token from the request headers or POST parameters. If the value doesn't match the token stored in the session, this function throws a PermissionDenied error.

For details, see the "AJAX CSRF protection" section of Yesod.Core.Handler.

Since 1.4.14

JS loaders

data ScriptLoadPosition master

Constructors

BottomOfBody

BottomOfHeadBlocking

BottomOfHeadAsync (BottomOfHeadAsync master)

type BottomOfHeadAsync master

Arguments

 = [Text]

urls to load asynchronously

-> Maybe (HtmlUrl (Route master))

widget of js to run on async completion

-> HtmlUrl (Route master)

widget to insert at the bottom of head

Subsites

class MonadResource m => MonadHandler m where

Associated Types

type HandlerSite m

Methods

liftHandlerT :: HandlerT (HandlerSite m) IO a -> m a

Instances

MonadHandler m => MonadHandler (MaybeT m)

MonadHandler m => MonadHandler (ListT m)

MonadHandler m => MonadHandler (IdentityT m)

(Monoid w, MonadHandler m) => MonadHandler (WriterT w m)

(Monoid w, MonadHandler m) => MonadHandler (WriterT w m)

MonadHandler m => MonadHandler (StateT s m)

MonadHandler m => MonadHandler (StateT s m)

MonadHandler m => MonadHandler (ReaderT r m)

(Error e, MonadHandler m) => MonadHandler (ErrorT e m)

MonadResourceBase m => MonadHandler (WidgetT site m)

MonadResourceBase m => MonadHandler (HandlerT site m)

MonadHandler m => MonadHandler (ConduitM i o m)

(Monoid w, MonadHandler m) => MonadHandler (RWST r w s m)

(Monoid w, MonadHandler m) => MonadHandler (RWST r w s m)

MonadHandler m => MonadHandler (Pipe l i o u m)

class MonadHandler m => MonadWidget m where

Methods

liftWidgetT :: WidgetT (HandlerSite m) IO a -> m a

Instances

MonadWidget m => MonadWidget (MaybeT m)

MonadWidget m => MonadWidget (ListT m)

MonadWidget m => MonadWidget (IdentityT m)

(Monoid w, MonadWidget m) => MonadWidget (WriterT w m)

(Monoid w, MonadWidget m) => MonadWidget (WriterT w m)

MonadWidget m => MonadWidget (StateT s m)

MonadWidget m => MonadWidget (StateT s m)

MonadWidget m => MonadWidget (ReaderT r m)

(Error e, MonadWidget m) => MonadWidget (ErrorT e m)

MonadResourceBase m => MonadWidget (WidgetT site m)

MonadWidget m => MonadWidget (ConduitM i o m)

(Monoid w, MonadWidget m) => MonadWidget (RWST r w s m)

(Monoid w, MonadWidget m) => MonadWidget (RWST r w s m)

MonadWidget m => MonadWidget (Pipe l i o u m)

getRouteToParent :: Monad m => HandlerT child (HandlerT parent m) (Route child -> Route parent)

defaultLayoutSub :: Yesod parent => WidgetT child IO () -> HandlerT child (HandlerT parent IO) Html

Approot

guessApproot :: Approot site

Guess the approot based on request headers. For more information, see Network.Wai.Middleware.Approot

In the case of headers being unavailable, it falls back to ApprootRelative

Since 1.4.16

guessApprootOr :: Approot site -> Approot site

Guess the approot based on request headers, with fall back to the specified AppRoot.

Since 1.4.16

getApprootText :: Approot site -> site -> Request -> Text

Get the textual application root from an Approot value.

Since 1.4.17

Misc

yesodVersion :: String

yesodRender

Arguments

:: Yesod y

=> y

-> ResolvedApproot

-> Route y

-> [(Text, Text)]

url query string

-> Text

runFakeHandler :: (Yesod site, MonadIO m) => SessionMap -> (site -> Logger) -> site -> HandlerT site IO a -> m (Either ErrorResponse a)

Deprecated: import runFakeHandler from Yesod.Core.Unsafe

LiteApp

newtype LiteApp

Constructors

LiteApp

Fields

unLiteApp :: Method -> [Text] -> Maybe (LiteHandler TypedContent)

Instances

Monoid LiteApp

ParseRoute LiteApp

RenderRoute LiteApp

Yesod LiteApp

YesodDispatch LiteApp

Eq (Route LiteApp)

Ord (Route LiteApp)

Read (Route LiteApp)

Show (Route LiteApp)

data Route LiteApp = LiteAppRoute [Text]

type LiteHandler = HandlerT LiteApp IO

type LiteWidget = WidgetT LiteApp IO

liteApp :: Writer LiteApp () -> LiteApp

dispatchTo :: ToTypedContent a => LiteHandler a -> Writer LiteApp ()

onMethod :: Method -> Writer LiteApp () -> Writer LiteApp ()

onStatic :: Text -> Writer LiteApp () -> Writer LiteApp ()

withDynamic :: PathPiece p => (p -> Writer LiteApp ()) -> Writer LiteApp ()

withDynamicMulti :: PathMultiPiece ps => (ps -> Writer LiteApp ()) -> Writer LiteApp ()

Low-level

yesodRunner :: (ToTypedContent res, Yesod site) => HandlerT site IO res -> YesodRunnerEnv site -> Maybe (Route site) -> Application

Re-exports

module Yesod.Core.Content

module Yesod.Core.Dispatch

module Yesod.Core.Handler

module Yesod.Core.Widget

module Yesod.Core.Json

module Text.Shakespeare.I18N

putTime :: UTCTime -> Put

getTime :: Get UTCTime

formatW3 :: UTCTime -> Text

Format a UTCTime in W3 format.

formatRFC1123 :: UTCTime -> Text

Format as per RFC 1123.

formatRFC822 :: UTCTime -> Text

Format as per RFC 822.

getCurrentMaxExpiresRFC1123 :: IO Text

Get the time 365 days from now in RFC 1123 format. For use as an expiry date on a resource that never expires. See RFC 2616 section 14.21 for details.

module Text.Blaze.Html

class MonadTrans t where

The class of monad transformers. Instances should satisfy the following laws, which state that lift is a monad transformation:

• lift . return = return

• lift (m >>= f) = lift m >>= (lift . f)

Methods

lift :: Monad m => m a -> t m a

Lift a computation from the argument monad to the constructed monad.

Instances

MonadTrans MaybeT

MonadTrans CatchT

MonadTrans NoLoggingT

MonadTrans LoggingT

MonadTrans ListT

MonadTrans ResourceT

MonadTrans IdentityT

Monoid w => MonadTrans (WriterT w)

Monoid w => MonadTrans (WriterT w)

MonadTrans (StateT s)

MonadTrans (StateT s)

MonadTrans (ReaderT r)

Error e => MonadTrans (ErrorT e)

MonadTrans (ContT r)

MonadTrans (ExceptT e)

MonadTrans (WidgetT site)

MonadTrans (HandlerT site)

MonadTrans (ConduitM i o)

Monoid w => MonadTrans (RWST r w s)

Monoid w => MonadTrans (RWST r w s)

MonadTrans (Pipe l i o u)

class Monad m => MonadIO m where

Monads in which IO computations may be embedded. Any monad built by applying a sequence of monad transformers to the IO monad will be an instance of this class.

Instances should satisfy the following laws, which state that liftIO is a transformer of monads:

• liftIO . return = return

• liftIO (m >>= f) = liftIO m >>= (liftIO . f)

Methods

liftIO :: IO a -> m a

Lift a computation from the IO monad.

Instances

MonadIO IO

MonadIO m => MonadIO (MaybeT m)

MonadIO m => MonadIO (CatchT m)

MonadIO m => MonadIO (NoLoggingT m)

MonadIO m => MonadIO (LoggingT m)

MonadIO m => MonadIO (ListT m)

MonadIO m => MonadIO (ResourceT m)

MonadIO m => MonadIO (IdentityT m)

(Monoid w, MonadIO m) => MonadIO (WriterT w m)

(Monoid w, MonadIO m) => MonadIO (WriterT w m)

MonadIO m => MonadIO (StateT s m)

MonadIO m => MonadIO (StateT s m)

MonadIO m => MonadIO (ReaderT r m)

(Error e, MonadIO m) => MonadIO (ErrorT e m)

MonadIO m => MonadIO (ContT r m)

MonadIO m => MonadIO (ExceptT e m)

MonadIO m => MonadIO (WidgetT site m)

MonadIO m => MonadIO (HandlerT site m)

MonadIO m => MonadIO (ConduitM i o m)

(Monoid w, MonadIO m) => MonadIO (RWST r w s m)

(Monoid w, MonadIO m) => MonadIO (RWST r w s m)

MonadIO m => MonadIO (Pipe l i o u m)

class (Applicative b, Applicative m, Monad b, Monad m) => MonadBase b m | m -> b where

Methods

liftBase :: b α -> m α

Lift a computation from the base monad

Instances

MonadBase [] []

MonadBase IO IO

MonadBase Maybe Maybe

MonadBase Identity Identity

MonadBase STM STM

MonadBase b m => MonadBase b (ResourceT m)

MonadBase b m => MonadBase b (NoLoggingT m)

MonadBase b m => MonadBase b (LoggingT m)

MonadBase b m => MonadBase b (MaybeT m)

MonadBase b m => MonadBase b (ListT m)

MonadBase b m => MonadBase b (IdentityT m)

(Monoid w, MonadBase b m) => MonadBase b (WriterT w m)

(Monoid w, MonadBase b m) => MonadBase b (WriterT w m)

MonadBase b m => MonadBase b (StateT s m)

MonadBase b m => MonadBase b (StateT s m)

MonadBase b m => MonadBase b (ReaderT r m)

MonadBase b m => MonadBase b (ExceptT e m)

(Error e, MonadBase b m) => MonadBase b (ErrorT e m)

MonadBase b m => MonadBase b (ContT r m)

MonadBase b m => MonadBase b (HandlerT site m)

MonadBase b m => MonadBase b (WidgetT site m)

MonadBase base m => MonadBase base (ConduitM i o m)

(Monoid w, MonadBase b m) => MonadBase b (RWST r w s m)

(Monoid w, MonadBase b m) => MonadBase b (RWST r w s m)

MonadBase base m => MonadBase base (Pipe l i o u m)

MonadBase ((->) r) ((->) r)

MonadBase (Either e) (Either e)

MonadBase (ST s) (ST s)

MonadBase (ST s) (ST s)

class MonadBase b m => MonadBaseControl b m | m -> b

Minimal complete definition

liftBaseWith, restoreM

Instances

MonadBaseControl [] []

MonadBaseControl IO IO

MonadBaseControl Maybe Maybe

MonadBaseControl Identity Identity

MonadBaseControl STM STM

MonadBaseControl b m => MonadBaseControl b (ResourceT m)

MonadBaseControl b m => MonadBaseControl b (MaybeT m)

MonadBaseControl b m => MonadBaseControl b (ListT m)

MonadBaseControl b m => MonadBaseControl b (IdentityT m)

MonadBaseControl b m => MonadBaseControl b (NoLoggingT m)

MonadBaseControl b m => MonadBaseControl b (LoggingT m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (WriterT w m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (WriterT w m)

MonadBaseControl b m => MonadBaseControl b (StateT s m)

MonadBaseControl b m => MonadBaseControl b (StateT s m)

MonadBaseControl b m => MonadBaseControl b (ReaderT r m)

MonadBaseControl b m => MonadBaseControl b (ExceptT e m)

(Error e, MonadBaseControl b m) => MonadBaseControl b (ErrorT e m)

MonadBaseControl b m => MonadBaseControl b (HandlerT site m)

Note: although we provide a MonadBaseControl instance, lifted-base's fork function is incompatible with the underlying ResourceT system. Instead, if you must fork a separate thread, you should use resourceForkIO.

Using fork usually leads to an exception that says "Control.Monad.Trans.Resource.register': The mutable state is being accessed after cleanup. Please contact the maintainers."

MonadBaseControl b m => MonadBaseControl b (WidgetT site m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (RWST r w s m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (RWST r w s m)

MonadBaseControl ((->) r) ((->) r)

MonadBaseControl (Either e) (Either e)

MonadBaseControl (ST s) (ST s)

MonadBaseControl (ST s) (ST s)

class (MonadThrow m, MonadIO m, Applicative m, MonadBase IO m) => MonadResource m where

A Monad which allows for safe resource allocation. In theory, any monad transformer stack included a ResourceT can be an instance of MonadResource.

Note: runResourceT has a requirement for a MonadBaseControl IO m monad, which allows control operations to be lifted. A MonadResource does not have this requirement. This means that transformers such as ContT can be an instance of MonadResource. However, the ContT wrapper will need to be unwrapped before calling runResourceT.

Since 0.3.0

Methods

liftResourceT :: ResourceT IO a -> m a

Lift a ResourceT IO action into the current Monad.

Since 0.4.0

Instances

MonadResource m => MonadResource (MaybeT m)

MonadResource m => MonadResource (NoLoggingT m)

MonadResource m => MonadResource (LoggingT m)

MonadResource m => MonadResource (ListT m)

(MonadThrow m, MonadBase IO m, MonadIO m, Applicative m) => MonadResource (ResourceT m)

MonadResource m => MonadResource (IdentityT m)

(Monoid w, MonadResource m) => MonadResource (WriterT w m)

(Monoid w, MonadResource m) => MonadResource (WriterT w m)

MonadResource m => MonadResource (StateT s m)

MonadResource m => MonadResource (StateT s m)

MonadResource m => MonadResource (ReaderT r m)

(Error e, MonadResource m) => MonadResource (ErrorT e m)

MonadResource m => MonadResource (ContT r m)

MonadResource m => MonadResource (ExceptT e m)

(Applicative m, MonadIO m, MonadBase IO m, MonadThrow m) => MonadResource (WidgetT site m)

(MonadIO m, MonadBase IO m, MonadThrow m) => MonadResource (HandlerT site m)

MonadResource m => MonadResource (ConduitM i o m)

(Monoid w, MonadResource m) => MonadResource (RWST r w s m)

(Monoid w, MonadResource m) => MonadResource (RWST r w s m)

MonadResource m => MonadResource (Pipe l i o u m)

class Monad m => MonadLogger m

A Monad which has the ability to log messages in some manner.

Instances

MonadLogger m => MonadLogger (MaybeT m)

Monad m => MonadLogger (NoLoggingT m)

MonadIO m => MonadLogger (LoggingT m)

MonadLogger m => MonadLogger (ListT m)

MonadLogger m => MonadLogger (ResourceT m)

MonadLogger m => MonadLogger (IdentityT m)

(MonadLogger m, Monoid w) => MonadLogger (WriterT w m)

(MonadLogger m, Monoid w) => MonadLogger (WriterT w m)

MonadLogger m => MonadLogger (StateT s m)

MonadLogger m => MonadLogger (StateT s m)

MonadLogger m => MonadLogger (ReaderT r m)

(MonadLogger m, Error e) => MonadLogger (ErrorT e m)

MonadLogger m => MonadLogger (ContT r m)

MonadLogger m => MonadLogger (ExceptT e m)

MonadIO m => MonadLogger (WidgetT site m)

MonadIO m => MonadLogger (HandlerT site m)

MonadLogger m => MonadLogger (ConduitM i o m)

(MonadLogger m, Monoid w) => MonadLogger (RWST r w s m)

(MonadLogger m, Monoid w) => MonadLogger (RWST r w s m)

MonadLogger m => MonadLogger (Pipe l i o u m)

Commonly referenced functions/datatypes

type Application = Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived

The WAI application.

Note that, since WAI 3.0, this type is structured in continuation passing style to allow for proper safe resource handling. This was handled in the past via other means (e.g., ResourceT). As a demonstration:

app :: Application
app req respond = bracket_
    (putStrLn "Allocating scarce resource")
    (putStrLn "Cleaning up")
    (respond $ responseLBS status200 [] "Hello World")

Utilities

showIntegral :: Integral a => a -> String

readIntegral :: Num a => String -> Maybe a

Shakespeare

Hamlet

hamlet :: QuasiQuoter

shamlet :: QuasiQuoter

xhamlet :: QuasiQuoter

type HtmlUrl url = Render url -> Html

A function generating an Html given a URL-rendering function.

Julius

julius :: QuasiQuoter

type JavascriptUrl url = (url -> [(Text, Text)] -> Text) -> Javascript

Return type of template-reading functions.

renderJavascriptUrl :: (url -> [(Text, Text)] -> Text) -> JavascriptUrl url -> Text

render with route interpolation. If using this module standalone, apart from type-safe routes, a dummy renderer can be used:

renderJavascriptUrl (\_ _ -> undefined) javascriptUrl

When using Yesod, a renderer is generated for you, which can be accessed within the GHandler monad: getUrlRenderParams.

Cassius/Lucius

cassius :: QuasiQuoter

lucius :: QuasiQuoter

>>> renderCss ([lucius|foo{bar:baz}|] undefined)
"foo{bar:baz}"

type CssUrl url = (url -> [(Text, Text)] -> Text) -> Css

renderCssUrl :: (url -> [(Text, Text)] -> Text) -> CssUrl url -> Text