Servant.API.ResponseHeaders

This module provides facilities for adding headers to a response.

>>> let headerVal = addHeader "some-url" 5 :: Headers '[Header "Location" String] Int

The value is added to the header specified by the type (Location in the example above).

Documentation

data Headers ls a

Response Header objects. You should never need to construct one directly. Instead, use addOptionalHeader.

Constructors

Headers

Fields

• getResponse :: a

  The underlying value of a Headers

• getHeadersHList :: HList ls

  HList of headers.

Instances

(KnownSymbol h, ToHttpApiData v) => AddHeader h v (Headers ((:) * fst rest) a) (Headers ((:) * (Header h v) ((:) * fst rest)) a)

Methods

addOptionalHeader :: Header h v -> Headers ((* ': fst) rest) a -> Headers ((* ': Header h v) ((* ': fst) rest)) a

Functor (Headers ls)

Methods

fmap :: (a -> b) -> Headers ls a -> Headers ls b

(<$) :: a -> Headers ls b -> Headers ls a

(KnownSymbol h, GetHeaders (HList rest), ToHttpApiData v) => GetHeaders (Headers ((:) * (Header h v) rest) a)

Methods

getHeaders :: Headers ((* ': Header h v) rest) a -> [Header]

GetHeaders (Headers ([] *) a)

Methods

getHeaders :: Headers [*] a -> [Header]

class AddHeader h v orig new | h v orig -> new, new -> h, new -> v, new -> orig

Minimal complete definition

addOptionalHeader

Instances

(KnownSymbol h, ToHttpApiData v, (~) * new (Headers ((:) * (Header h v) ([] *)) a)) => AddHeader h v a new

Methods

addOptionalHeader :: Header h v -> a -> new

(KnownSymbol h, ToHttpApiData v) => AddHeader h v (Headers ((:) * fst rest) a) (Headers ((:) * (Header h v) ((:) * fst rest)) a)

Methods

addOptionalHeader :: Header h v -> Headers ((* ': fst) rest) a -> Headers ((* ': Header h v) ((* ': fst) rest)) a

addHeader :: AddHeader h v orig new => v -> orig -> new

addHeader adds a header to a response. Note that it changes the type of the value in the following ways:

1. A simple value is wrapped in "Headers '[hdr]":

>>> let example1 = addHeader 5 "hi" :: Headers '[Header "someheader" Int] String;
>>> getHeaders example1
[("someheader","5")]

1. A value that already has a header has its new header *prepended* to the existing list:

>>> let example1 = addHeader 5 "hi" :: Headers '[Header "someheader" Int] String;
>>> let example2 = addHeader True example1 :: Headers '[Header "1st" Bool, Header "someheader" Int] String
>>> getHeaders example2
[("1st","true"),("someheader","5")]

Note that while in your handlers type annotations are not required, since the type can be inferred from the API type, in other cases you may find yourself needing to add annotations.

noHeader :: AddHeader h v orig new => orig -> new

Deliberately do not add a header to a value.

>>> let example1 = noHeader "hi" :: Headers '[Header "someheader" Int] String
>>> getHeaders example1
[]

class BuildHeadersTo hs where

Minimal complete definition

buildHeadersTo

Methods

buildHeadersTo :: [Header] -> HList hs

Note: if there are multiple occurences of a header in the argument, the values are interspersed with commas before deserialization (see RFC2616 Sec 4.2)

Instances

BuildHeadersTo ([] *)

Methods

buildHeadersTo :: [Header] -> HList [*]

(FromHttpApiData v, BuildHeadersTo xs, KnownSymbol h) => BuildHeadersTo ((:) * (Header h v) xs)

Methods

buildHeadersTo :: [Header] -> HList ((* ': Header h v) xs)

class GetHeaders ls where

Minimal complete definition

getHeaders

Methods

getHeaders :: ls -> [Header]

Instances

(KnownSymbol h, ToHttpApiData x, GetHeaders (HList xs)) => GetHeaders (HList ((:) * (Header h x) xs))

Methods

getHeaders :: HList ((* ': Header h x) xs) -> [Header]

GetHeaders (HList ([] *))

Methods

getHeaders :: HList [*] -> [Header]

(KnownSymbol h, GetHeaders (HList rest), ToHttpApiData v) => GetHeaders (Headers ((:) * (Header h v) rest) a)

Methods

getHeaders :: Headers ((* ': Header h v) rest) a -> [Header]

GetHeaders (Headers ([] *) a)

Methods

getHeaders :: Headers [*] a -> [Header]

type family HeaderValMap (f :: * -> *) (xs :: [*]) where ...

Equations

HeaderValMap f '[] = '[]

HeaderValMap f (Header h x ': xs) = Header h (f x) ': HeaderValMap f xs

data HList a where

Constructors

HNil :: HList '[]

HCons :: Header h x -> HList xs -> HList (Header h x ': xs)

Instances

(KnownSymbol h, ToHttpApiData x, GetHeaders (HList xs)) => GetHeaders (HList ((:) * (Header h x) xs))

Methods

getHeaders :: HList ((* ': Header h x) xs) -> [Header]

GetHeaders (HList ([] *))

Methods

getHeaders :: HList [*] -> [Header]