HTTP clients – Haskell – Aelve Guidehttps://guide.aelve.com/haskell/feed/category/lohjgbh42018-06-14T04:16:33Zm0i2mls5wreq2018-06-14T04:16:33Z<h1> <span class="item-name">wreq</span>
(<a href="https://hackage.haskell.org/package/wreq">Hackage</a>)
</h1><h2>Pros</h2><ul></ul><h2>Cons</h2><ul></ul><h2>Notes</h2><h1><span id="item-notes-m0i2mls5-links"></span>Links</h1><p><a href="http://www.serpentine.com/wreq/">wreq homepage (and tutorial)</a></p>
<h1><span id="item-notes-m0i2mls5-imports"></span>Imports</h1><p>import Control.Lens
import Network.Wreq</p>
<h1><span id="item-notes-m0i2mls5-usage"></span>Usage</h1><p><a href="http://bitemyapp.com/posts/2016-02-06-haskell-is-not-trivial-not-unfair.html">bitemyapp walkthrough of a wreq usage</a></p>
<h1><span id="item-notes-m0i2mls5-gotchas"></span>Gotchas</h1><p>Common mistakes and non-obvious things</p>
lk98x0lereq2018-06-14T04:16:30Z<h1> <span class="item-name">req</span>
(<a href="https://hackage.haskell.org/package/req">Hackage</a>)
</h1><h2>Pros</h2><ul></ul><h2>Cons</h2><ul></ul><h2>Notes</h2><h1><span id="item-notes-lk98x0le-links"></span>Links</h1><p>Links to tutorials, blog posts, etc.</p>
<h1><span id="item-notes-lk98x0le-imports"></span>Imports</h1><div class="sourceCode"><pre class="sourceCode"><code class="sourceCode"><span class="kw">import qualified</span> <span class="dt">Network.HTTP.Req</span> <span class="kw">as</span> <span class="dt">R</span></code></pre></div>
<h1><span id="item-notes-lk98x0le-usage"></span>Usage</h1><p>[ see the hackage page for a commented example ]</p>
<h1><span id="item-notes-lk98x0le-gotchas"></span>Gotchas</h1><p>The <a href="urrrrrrrrrl">req function</a> uses type tricks that make [R.GET, R.PUT] not type-check. If you want to pass around request parameters use a GADT like:</p>
<div class="sourceCode"><pre class="sourceCode"><code class="sourceCode"><span class="co">-- | A Request to be compiled into an IO action. Does not specify return type</span>
<span class="kw">data</span> <span class="dt">Request</span> <span class="kw">where</span>
<span class="dt">Delete</span><span class="ot"> ::</span> <span class="dt">R.Url</span> <span class="ch">'R.Https -> Option -> Request</span>
<span class="dt">Get</span><span class="ot"> ::</span> <span class="dt">R.Url</span> <span class="ch">'R.Https -> Option -> Request</span>
<span class="dt">Patch</span><span class="ot"> ::</span> <span class="dt">R.HttpBody</span> a <span class="ot">=></span> <span class="dt">R.Url</span> <span class="ch">'R.Https -> a -> Option -> Request</span>
<span class="dt">Put</span><span class="ot"> ::</span> <span class="dt">R.HttpBody</span> a <span class="ot">=></span> <span class="dt">R.Url</span> <span class="ch">'R.Https -> a -> Option -> Request</span>
<span class="dt">Post</span><span class="ot"> ::</span> <span class="dt">R.HttpBody</span> a <span class="ot">=></span> <span class="dt">R.Url</span> <span class="ch">'R.Https -> a -> Option -> Request</span></code></pre></div>
<p>The library throws exceptions on non-2XX response codes (eg 404). If this is not desired edit
<a href="https://hackage.haskell.org/package/req-1.1.0/docs/Network-HTTP-Req.html#v:httpConfigCheckResponse">httpConfigCheckResponse</a> to something like:</p>
<div class="sourceCode"><pre class="sourceCode"><code class="sourceCode"><span class="kw">instance</span> <span class="dt">R.MonadHttp</span> <span class="dt">MyCustomIOMonad</span> <span class="kw">where</span> <span class="co">-- or just IO</span>
<span class="co">-- :: R.MonadHttp m => R.HttpException -> m a</span>
handleHttpException <span class="fu">=</span> throwIO
<span class="co">-- :: Req HttpConfig</span>
getHttpConfig <span class="fu">=</span> pure <span class="fu">$</span> def { R.httpConfigCheckResponse <span class="fu">=</span> \_ _ _ <span class="ot">-></span> <span class="dt">Nothing</span> }</code></pre></div>