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45 lines
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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.QueryParam</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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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Servant-API-QueryParam.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</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.QueryParam</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:QueryParam">QueryParam</a> sym a</li><li class="src short"><span class="keyword">data</span> <a href="#t:QueryParams">QueryParams</a> sym a</li><li class="src short"><span class="keyword">data</span> <a href="#t:QueryFlag">QueryFlag</a> sym</li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:QueryParam" class="def">QueryParam</a> sym a <a href="src/Servant-API-QueryParam.html#QueryParam" class="link">Source</a></p><div class="doc"><p>Lookup the value associated to the <code>sym</code> query string parameter
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and try to extract it as a value of type <code>a</code>.</p><p>Example:</p><pre>-- /books?author=<author name>
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type MyApi = "books" :> QueryParam "author" Text :> Get [Book]</pre></div><div class="subs instances"><p id="control.i:QueryParam" class="caption collapser" onclick="toggleSection('i:QueryParam')">Instances</p><div id="section.i:QueryParam" 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-QueryParam.html#t:QueryParam">QueryParam</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><code><a href="Servant-API-QueryParam.html#t:QueryParam">QueryParam</a></code> "author" Text</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 type <code><code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Maybe.html#t:Maybe">Maybe</a></code> <code>Text</code></code>.</p><p>This lets servant worry about looking it up in the query string
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and turning it into a value of the type you specify, enclosed
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in <code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Maybe.html#t:Maybe">Maybe</a></code>, because it may not be there and servant would then
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hand you <code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Maybe.html#v:Nothing">Nothing</a></code>.</p><p>You can control how it'll be converted from <code>Text</code> to your type
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by simply providing an instance of <code><a href="Servant-Common-Text.html#t:FromText">FromText</a></code> for your type.</p><p>Example:</p><pre>type MyApi = "books" :> QueryParam "author" Text :> Get [Book]
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server :: Server MyApi
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server = getBooksBy
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where getBooksBy :: Maybe Text -> EitherT (Int, String) IO [Book]
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getBooksBy Nothing = ...return all books...
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getBooksBy (Just author) = ...return books by the given author...</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-QueryParam.html#t:QueryParam">QueryParam</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 class="top"><p class="src"><span class="keyword">data</span> <a name="t:QueryParams" class="def">QueryParams</a> sym a <a href="src/Servant-API-QueryParam.html#QueryParams" class="link">Source</a></p><div class="doc"><p>Lookup the values associated to the <code>sym</code> query string parameter
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and try to extract it as a value of type <code>[a]</code>. This is typically
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meant to support query string parameters of the form
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<code>param[]=val1&param[]=val2</code> and so on. Note that servant doesn't actually
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require the <code>[]</code>s and will fetch the values just fine with
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<code>param=val1&param=val2</code>, too.</p><p>Example:</p><pre>-- /books?authors[]=<author1>&authors[]=<author2>&...
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type MyApi = "books" :> QueryParams "authors" Text :> Get [Book]</pre></div><div class="subs instances"><p id="control.i:QueryParams" class="caption collapser" onclick="toggleSection('i:QueryParams')">Instances</p><div id="section.i:QueryParams" 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-QueryParam.html#t:QueryParams">QueryParams</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><code><a href="Servant-API-QueryParam.html#t:QueryParams">QueryParams</a></code> "authors" Text</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 type <code>[<code>Text</code>]</code>.</p><p>This lets servant worry about looking up 0 or more values in the query string
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associated to <code>authors</code> and turning each of them into a value of
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the type you specify.</p><p>You can control how the individual values are converted from <code>Text</code> to your type
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by simply providing an instance of <code><a href="Servant-Common-Text.html#t:FromText">FromText</a></code> for your type.</p><p>Example:</p><pre>type MyApi = "books" :> QueryParams "authors" Text :> Get [Book]
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server :: Server MyApi
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server = getBooksBy
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where getBooksBy :: [Text] -> EitherT (Int, String) IO [Book]
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getBooksBy authors = ...return all books by these authors...</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-QueryParam.html#t:QueryParams">QueryParams</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] -> <a href="Servant-Server.html#t:Server">Server</a> sublayout</td><td class="doc empty"> </td></tr></table></div></div></div><div class="top"><p class="src"><span class="keyword">data</span> <a name="t:QueryFlag" class="def">QueryFlag</a> sym <a href="src/Servant-API-QueryParam.html#QueryFlag" class="link">Source</a></p><div class="doc"><p>Lookup a potentially value-less query string parameter
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with boolean semantics. If the param <code>sym</code> is there without any value,
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or if it's there with value "true" or "1", it's interpreted as <code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Bool.html#v:True">True</a></code>.
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Otherwise, it's interpreted as <code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Bool.html#v:False">False</a></code>.</p><p>Example:</p><pre>-- /books?published
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type MyApi = "books" :> QueryFlag "published" :> Get [Book]</pre></div><div class="subs instances"><p id="control.i:QueryFlag" class="caption collapser" onclick="toggleSection('i:QueryFlag')">Instances</p><div id="section.i:QueryFlag" 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-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-QueryParam.html#t:QueryFlag">QueryFlag</a> <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-TypeLits.html#t:Symbol">Symbol</a> sym) sublayout)</td><td class="doc"><p>If you use <code><code><a href="Servant-API-QueryParam.html#t:QueryFlag">QueryFlag</a></code> "published"</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 type <code><a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Bool.html#t:Bool">Bool</a></code>.</p><p>Example:</p><pre>type MyApi = "books" :> QueryFlag "published" :> Get [Book]
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server :: Server MyApi
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server = getBooks
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where getBooks :: Bool -> EitherT (Int, String) IO [Book]
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getBooks onlyPublished = ...return all books, or only the ones that are already published, depending on the argument...</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-QueryParam.html#t:QueryFlag">QueryFlag</a> <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-TypeLits.html#t:Symbol">Symbol</a> sym) sublayout) = <a href="https://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Bool.html#t:Bool">Bool</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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