21 lines
4.2 KiB
HTML
21 lines
4.2 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Servant.API.Header</title><link href="ocean.css" rel="stylesheet" type="text/css" title="Ocean" /><script src="haddock-util.js" type="text/javascript"></script><script type="text/javascript">//<![CDATA[
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window.onload = function () {pageLoad();setSynopsis("mini_Servant-API-Header.html");};
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//]]>
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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Servant-API-Header.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">servant-0.2: A family of combinators for defining webservices APIs and serving them</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Safe Haskell</th><td>None</td></tr><tr><th>Language</th><td>Haskell2010</td></tr></table><p class="caption">Servant.API.Header</p></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><span class="keyword">data</span> <a href="#t:Header">Header</a> sym a</li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:Header" class="def">Header</a> sym a <a href="src/Servant-API-Header.html#Header" class="link">Source</a></p><div class="doc"><p>Extract the given header's value as a value of type <code>a</code>.</p><p>Example:</p><pre>newtype Referer = Referer Text
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deriving (Eq, Show, FromText, ToText)
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-- GET /view-my-referer
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type MyApi = "view-my-referer" :> Header "from" Referer :> Get Referer</pre></div><div class="subs instances"><p id="control.i:Header" class="caption collapser" onclick="toggleSection('i:Header')">Instances</p><div id="section.i:Header" class="show"><table><tr><td class="src">(<a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-TypeLits.html#t:KnownSymbol">KnownSymbol</a> sym, <a href="Servant-Common-Text.html#t:FromText">FromText</a> a, <a href="Servant-Server.html#t:HasServer">HasServer</a> sublayout) => <a href="Servant-Server.html#t:HasServer">HasServer</a> (<a href="Servant-API-Sub.html#t::-62-">(:>)</a> * (<a href="Servant-API-Header.html#t:Header">Header</a> <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-TypeLits.html#t:Symbol">Symbol</a> * sym a) sublayout)</td><td class="doc"><p>If you use <code><a href="Servant-API-Header.html#t:Header">Header</a></code> in one of the endpoints for your API,
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this automatically requires your server-side handler to be a function
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that takes an argument of the type specified by <code><a href="Servant-API-Header.html#t:Header">Header</a></code>.
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This lets servant worry about extracting it from the request and turning
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it into a value of the type you specify.</p><p>All it asks is for a <code><a href="Servant-Common-Text.html#t:FromText">FromText</a></code> instance.</p><p>Example:</p><pre>newtype Referer = Referer Text
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deriving (Eq, Show, FromText, ToText)
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-- GET /view-my-referer
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type MyApi = "view-my-referer" :> Header "Referer" Referer :> Get Referer
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server :: Server MyApi
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server = viewReferer
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where viewReferer :: Referer -> EitherT (Int, String) IO referer
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viewReferer referer = return referer</pre></td></tr><tr><td class="src"><span class="keyword">type</span> <a href="Servant-Server.html#t:Server">Server</a> (<a href="Servant-API-Sub.html#t::-62-">(:>)</a> * (<a href="Servant-API-Header.html#t:Header">Header</a> <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-TypeLits.html#t:Symbol">Symbol</a> * sym a) sublayout) = <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Maybe.html#t:Maybe">Maybe</a> a -> <a href="Servant-Server.html#t:Server">Server</a> sublayout</td><td class="doc empty"> </td></tr></table></div></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.15.0</p></div></body></html>
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