Safe Haskell | None |
---|---|
Language | Haskell98 |
happstack-foundation
provides a type-safe environment for Haskell web development. It builds on top of:
- happstack-server - an HTTP server
- HSP - HTML Templating
- web-routes - type-safe URL routing
- reform - type-safe form composition and validation
- acid-state - native Haskell persistent database
An example application can be found here:
A screencast can be found here:
http://www.youtube.com/watch?v=7Wmszk4wZxQ
happstack-foundation
itself is not yet documented in the Happstack Crash Course. However, all of the components that it uses are:
- data AcidConfig st where
- AcidLocal :: (IsAcidic st, Typeable st) => Maybe FilePath -> st -> AcidConfig (AcidState st)
- AcidUsing :: st -> AcidConfig st
- data FoundationConf = FoundationConf {
- httpConf :: Conf
- bodyPolicy :: BodyPolicy
- defaultConf :: FoundationConf
- type FoundationT url acidState requestState m = XMLGenT (FoundationT' url acidState requestState m)
- type FoundationT' url acidState requestState m = RouteT url (StateT (AppState url acidState requestState) (ServerPartT m))
- type FoundationForm url acidState requestState m = Form (FoundationT url acidState requestState m) [Input] AppError [FoundationT url acidState requestState m XML] ()
- whereami :: (Functor m, Monad m) => FoundationT url acidState requestState m url
- getRequestState :: (Functor m, MonadState (AppState url acidState requestState) m) => m requestState
- setRequestState :: (Functor m, MonadState (AppState url acidState requestState) m) => requestState -> m ()
- modifyRequestState :: MonadState (AppState url acidState requestState) m => (requestState -> requestState) -> m ()
- defaultTemplate :: (Functor m, Monad m, XMLGenerator (FoundationT' url acidState requestState m), EmbedAsChild (FoundationT' url acidState requestState m) body, EmbedAsChild (FoundationT' url acidState requestState m) headers, XMLType (FoundationT' url acidState requestState m) ~ XML) => Text -> headers -> body -> FoundationT url acidState requestState m XML
- class HasAcidState m st where
- getAcidState :: m (AcidState st)
- query :: forall event m. (Functor m, MonadIO m, QueryEvent event, HasAcidState m (EventState event)) => event -> m (EventResult event)
- update :: forall event m. (Functor m, MonadIO m, UpdateEvent event, HasAcidState m (EventState event)) => event -> m (EventResult event)
- getAcidSt :: (Functor m, MonadState (AppState url acidState requestState) m) => m acidState
- simpleApp :: (ToMessage a, PathInfo url, Monad m) => (forall r. m r -> IO r) -> FoundationConf -> AcidConfig acidState -> requestState -> url -> Text -> (url -> FoundationT url acidState requestState m a) -> IO ()
- class Typeable * a => Data a where
- gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a
- gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a
- toConstr :: a -> Constr
- dataTypeOf :: a -> DataType
- dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c a)
- dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)
- gmapT :: (forall b. Data b => b -> b) -> a -> a
- gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
- gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
- gmapQ :: (forall d. Data d => d -> u) -> a -> [u]
- gmapQi :: Int -> (forall d. Data d => d -> u) -> a -> u
- gmapM :: Monad m => (forall d. Data d => d -> m d) -> a -> m a
- gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
- gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
- class Typeable a
- module Control.Applicative
- module Control.Monad.Reader
- module Control.Monad.State
- module Data.SafeCopy
- module Data.Acid
- module Happstack.Server
- module HSP
- module Web.Routes
- module Web.Routes.Happstack
- module Web.Routes.TH
- module Text.Reform
- module Text.Reform.Happstack
- module Text.Reform.HSP.Text
- data AppError
- = AppCFE (CommonFormError [Input])
- | TextError Text
Configuration
data AcidConfig st where Source
configuration information for our acid-state database
AcidLocal :: (IsAcidic st, Typeable st) => Maybe FilePath -> st -> AcidConfig (AcidState st) | |
AcidUsing :: st -> AcidConfig st |
data FoundationConf Source
configuration for server
defaultConf :: FoundationConf Source
configuration
Type Aliases
type FoundationT url acidState requestState m = XMLGenT (FoundationT' url acidState requestState m) Source
the FoundationT
monad
url
- the type-safe URL route typeacidState
- the type of the state value stored in acid-staterequestState
- a per-request state value that the developer can getsetmodifym
- inner monad
see also: whereami
, getRequestState
, setRequestState
, modifyRequestState
, simpleApp
type FoundationT' url acidState requestState m = RouteT url (StateT (AppState url acidState requestState) (ServerPartT m)) Source
similar to the FoundationT'
type alias, but without the XMLGenT
wrapper. This variant is most often used in class constraints.
type FoundationForm url acidState requestState m = Form (FoundationT url acidState requestState m) [Input] AppError [FoundationT url acidState requestState m XML] () Source
FoundationForm
is an alias for working with reform based Forms
FoundationT functions
whereami :: (Functor m, Monad m) => FoundationT url acidState requestState m url Source
returns the decoded url
from the Request
getRequestState :: (Functor m, MonadState (AppState url acidState requestState) m) => m requestState Source
get the requestState
value
setRequestState :: (Functor m, MonadState (AppState url acidState requestState) m) => requestState -> m () Source
set the requestState
value
modifyRequestState :: MonadState (AppState url acidState requestState) m => (requestState -> requestState) -> m () Source
set the requestState
value
HTML Template
defaultTemplate :: (Functor m, Monad m, XMLGenerator (FoundationT' url acidState requestState m), EmbedAsChild (FoundationT' url acidState requestState m) body, EmbedAsChild (FoundationT' url acidState requestState m) headers, XMLType (FoundationT' url acidState requestState m) ~ XML) => Text -> headers -> body -> FoundationT url acidState requestState m XML Source
default page template
acid-state
class HasAcidState m st where Source
HasAcidState
provides a single method getAcidState
which can be used to retrieve an AcidState
handle from the current monad.
getAcidState :: m (AcidState st) Source
HasAcidState (FoundationT' url acid reqSt m) acidSt => HasAcidState (XMLGenT (FoundationT' url acid reqSt m)) acidSt | |
(Functor m, Monad m) => HasAcidState (FoundationT url (AcidState acidState) requestState m) acidState |
query :: forall event m. (Functor m, MonadIO m, QueryEvent event, HasAcidState m (EventState event)) => event -> m (EventResult event) Source
wrapper around query from acid-state
This variant automatically gets the AcidState
handle from the monad
update :: forall event m. (Functor m, MonadIO m, UpdateEvent event, HasAcidState m (EventState event)) => event -> m (EventResult event) Source
wrapper around update from acid-state
This variant automatically gets the AcidState
handle from the monad
getAcidSt :: (Functor m, MonadState (AppState url acidState requestState) m) => m acidState Source
running
:: (ToMessage a, PathInfo url, Monad m) | |
=> (forall r. m r -> IO r) | function to flatten inner monad |
-> FoundationConf |
|
-> AcidConfig acidState |
|
-> requestState | initial |
-> url | default URL (ie, what does / map to) |
-> Text | the base URL for the site as seen by the outside world (or, at least, by your openid provider) (e.g. "http://example.org:8000", no trailing slash) |
-> (url -> FoundationT url acidState requestState m a) | handler |
-> IO () |
run the application
starts the database, listens for requests, etc.
re-exports
class Typeable * a => Data a where
The Data
class comprehends a fundamental primitive gfoldl
for
folding over constructor applications, say terms. This primitive can
be instantiated in several ways to map over the immediate subterms
of a term; see the gmap
combinators later in this class. Indeed, a
generic programmer does not necessarily need to use the ingenious gfoldl
primitive but rather the intuitive gmap
combinators. The gfoldl
primitive is completed by means to query top-level constructors, to
turn constructor representations into proper terms, and to list all
possible datatype constructors. This completion allows us to serve
generic programming scenarios like read, show, equality, term generation.
The combinators gmapT
, gmapQ
, gmapM
, etc are all provided with
default definitions in terms of gfoldl
, leaving open the opportunity
to provide datatype-specific definitions.
(The inclusion of the gmap
combinators as members of class Data
allows the programmer or the compiler to derive specialised, and maybe
more efficient code per datatype. Note: gfoldl
is more higher-order
than the gmap
combinators. This is subject to ongoing benchmarking
experiments. It might turn out that the gmap
combinators will be
moved out of the class Data
.)
Conceptually, the definition of the gmap
combinators in terms of the
primitive gfoldl
requires the identification of the gfoldl
function
arguments. Technically, we also need to identify the type constructor
c
for the construction of the result type from the folded term type.
In the definition of gmapQ
x combinators, we use phantom type
constructors for the c
in the type of gfoldl
because the result type
of a query does not involve the (polymorphic) type of the term argument.
In the definition of gmapQl
we simply use the plain constant type
constructor because gfoldl
is left-associative anyway and so it is
readily suited to fold a left-associative binary operation over the
immediate subterms. In the definition of gmapQr, extra effort is
needed. We use a higher-order accumulation trick to mediate between
left-associative constructor application vs. right-associative binary
operation (e.g., (:)
). When the query is meant to compute a value
of type r
, then the result type withing generic folding is r -> r
.
So the result of folding is a function to which we finally pass the
right unit.
With the -XDeriveDataTypeable
option, GHC can generate instances of the
Data
class automatically. For example, given the declaration
data T a b = C1 a b | C2 deriving (Typeable, Data)
GHC will generate an instance that is equivalent to
instance (Data a, Data b) => Data (T a b) where gfoldl k z (C1 a b) = z C1 `k` a `k` b gfoldl k z C2 = z C2 gunfold k z c = case constrIndex c of 1 -> k (k (z C1)) 2 -> z C2 toConstr (C1 _ _) = con_C1 toConstr C2 = con_C2 dataTypeOf _ = ty_T con_C1 = mkConstr ty_T "C1" [] Prefix con_C2 = mkConstr ty_T "C2" [] Prefix ty_T = mkDataType "Module.T" [con_C1, con_C2]
This is suitable for datatypes that are exported transparently.
:: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) | defines how nonempty constructor applications are folded. It takes the folded tail of the constructor application and its head, i.e., an immediate subterm, and combines them in some way. |
-> (forall g. g -> c g) | defines how the empty constructor application is folded, like the neutral / start element for list folding. |
-> a | structure to be folded. |
-> c a | result, with a type defined in terms of |
Left-associative fold operation for constructor applications.
The type of gfoldl
is a headache, but operationally it is a simple
generalisation of a list fold.
The default definition for gfoldl
is
, which is
suitable for abstract datatypes with no substructures.const
id
gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a
Unfolding constructor applications
Obtaining the constructor from a given datum. For proper terms, this is meant to be the top-level constructor. Primitive datatypes are here viewed as potentially infinite sets of values (i.e., constructors).
dataTypeOf :: a -> DataType
The outer type constructor of the type
dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c a)
Mediate types and unary type constructors.
In Data
instances of the form T a
, dataCast1
should be defined
as gcast1
.
The default definition is
, which is appropriate
for non-unary type constructors.const
Nothing
dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)
Mediate types and binary type constructors.
In Data
instances of the form T a b
, dataCast2
should be
defined as gcast2
.
The default definition is
, which is appropriate
for non-binary type constructors.const
Nothing
gmapT :: (forall b. Data b => b -> b) -> a -> a
A generic transformation that maps over the immediate subterms
The default definition instantiates the type constructor c
in the
type of gfoldl
to an identity datatype constructor, using the
isomorphism pair as injection and projection.
gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
A generic query with a left-associative binary operator
gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
A generic query with a right-associative binary operator
gmapQ :: (forall d. Data d => d -> u) -> a -> [u]
A generic query that processes the immediate subterms and returns a list of results. The list is given in the same order as originally specified in the declaratoin of the data constructors.
gmapQi :: Int -> (forall d. Data d => d -> u) -> a -> u
A generic query that processes one child by index (zero-based)
gmapM :: Monad m => (forall d. Data d => d -> m d) -> a -> m a
A generic monadic transformation that maps over the immediate subterms
The default definition instantiates the type constructor c
in
the type of gfoldl
to the monad datatype constructor, defining
injection and projection using return
and >>=
.
gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
Transformation of at least one immediate subterm does not fail
gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
Transformation of one immediate subterm with success
class Typeable a
The class Typeable
allows a concrete representation of a type to
be calculated.
module Control.Applicative
module Control.Monad.Reader
module Control.Monad.State
module Data.SafeCopy
module Data.Acid
module Happstack.Server
module HSP
module Web.Routes
module Web.Routes.Happstack
module Web.Routes.TH
module Text.Reform
module Text.Reform.Happstack
module Text.Reform.HSP.Text
Internals
an error type used with reform forms
IsString AppError | |
FormError AppError | |
(Functor m, Monad m) => EmbedAsChild (FoundationT' url acidState requestState m) AppError | |
type ErrorInputType AppError = [Input] |