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POWhat's the "big idea" behind compojure routes?
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  1. POWhat's the "big idea" behind compojure routes?
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    copied!<p>I'm new to Clojure and have been using Compojure to write a basic web application. I'm hitting a wall with Compojure's <code>defroutes</code> syntax, though, and I think I need to understand both the "how" and the "why" behind it all.</p> <p>It seems like a Ring-style application begins with an HTTP request map, then just passes the request through a series of middleware functions until it gets transformed into a response map, which gets sent back to the browser. This style seems too "low level" for developers, thus the need for a tool like Compojure. I can see this need for more abstractions in other software ecosystems as well, most notably with Python's WSGI.</p> <p>The problem is that I don't understand Compojure's approach. Let's take the following <code>defroutes</code> S-expression:</p> <pre><code>(defroutes main-routes (GET "/" [] (workbench)) (POST "/save" {form-params :form-params} (str form-params)) (GET "/test" [&amp; more] (str "&lt;pre&gt;" more "&lt;/pre&gt;")) (GET ["/:filename" :filename #".*"] [filename] (response/file-response filename {:root "./static"})) (ANY "*" [] "&lt;h1&gt;Page not found.&lt;/h1&gt;")) </code></pre> <p>I know that the key to understanding all of this lies within some macro voodoo, but I don't totally understand macros (yet). I've stared at the <code>defroutes</code> source for a long time, but just don't get it! What's going on here? Understanding the "big idea" will probably help me answer these specific questions:</p> <ol> <li>How do I access the Ring environment from within a routed function (e.g. the <code>workbench</code> function)? For example, say I wanted to access the HTTP_ACCEPT headers or some other part of the request/middleware?</li> <li>What's the deal with the destructuring (<code>{form-params :form-params}</code>)? What keywords are available for me when destructuring?</li> </ol> <p>I really like Clojure but I am so stumped!</p>
 

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