A lot of people have already heard that they should use Stuart Sierra’s component library to manage state in their Clojure applications. But most don’t know why and how you would incorporate it into your software. This how to guide will give you all the tools you need to start managing state in your Clojure software. What is component? Component is a Clojure library that can be thought of as a micro dependency injection framework. Read more...

Backstory I wrote an article on how I decided to go with Ruby instead of Clojure a while back. I moved my blog from Wordpress to Jekyll yesterday and think it’s time for an honest update. I also have a Node.js and Clojure comparison article if you’re also interested. It tells a different side of a similar story for people looking to pick between Javascript and Clojure. Read more...

When developing applications in Clojure, one thing you might need is to be able to somehow keep different settings for each environment. For instance, you might want to be able to have different database settings for each environment. This can be achieved with leiningen profiles: :profiles {:dev-overrides {} :dev [:dev-overrides {:dependencies [[com.cemerick/austin "0.1.5"] [com.cemerick/piggieback "0.1.4-SNAPSHOT"] [ring-mock "0.1.5"]] :plugins [[com.keminglabs/cljx "0.5.0"] [com.cemerick/austin "0.1.5"] [lein-cljsbuild "1.0.3"]]}] :test-overrides {} :test [:dev :test-overrides]} Assuming you have that :profiles sub-map somewhere in your project. Read more...

I haven't had many good ideas for blog posts, but I've gotten this bright idea to do tutorials/overviews of the libraries I use in Clojure. The first one is Prismatic's Schema. Schema is an awesome library once you understand it. Let's go over some of the more important concepts via the schema readme. The first thing that jumps out when you first see Schema is that it allows you to validate functions and data. Read more...

I recently added the function juxt to my toolbox in Clojure. A good pattern I've discovered is using juxt to perform operations on a data structure and destructuring its return value. (defn read-files [^String path] (let [data-files (find-data-files path) [prices receipts] ((juxt find-prices-file find-receipt-files) data-files)] {:prices (read-prices prices) :receipts (apply merge (read-receipts receipts))}))

Before we begin, make sure you can start a node.cljs repl first. One important thing I want to highlight is that you should have a stable version of node 0.12.X as the linked wiki page says. Additionally, you want to make sure you have npm installed so you can install node packages later on. Finally, I'm also assuming that you already have Clojure and Clojurescript setup with Leiningen. Let's begin. Read more...

I ran into an issue like usual. This time it seemed simple. I wanted to refer to a record that I def'd in another namespace. The problem is, you can't just do a :require and :refer it in regular Clojure. However, in Clojurescript this is how you would do it. What you have to do is :import it. And the key trick to keep in mind when using :import on records and Clojure namespaces is that dashes are converted to underscores like packages in Java. Read more...

I ran into an issue at work earlier this week. I needed to include a phone number validation library in the Clojurescript side. It was libphonenumber by Google, which meant it was compiled with the Google closure library. Great! That gets us halfway there. That classifies it as a third party library, meaning in lein-cljsbuild you would specify it under the :libs key instead of the :preamble, :externs, or :foreign-libs. I just want to make it clear that the :foreign-libs option is used for non Google closure code like jquery. Read more...

A neat trick I learned a few months back is that you can reset all of your Clojure namespaces in the repl you're working on if you're using Emacs + Cider. Just use M-x cider-refresh. That command 'refreshes' your repl by undefining the vars and reloading them. This way, if you have run-away code in your repl state, you can refresh it without doing a cider-restart. This comes in handy especially when you're writing tests with clojure. Read more...

I'm a Ruby, Clojure, and now Node.js developer. When I was doing Clojure, I had a REPL driven development style. Those of you that don't know what a REPL is, it's a read-eval-print-loop. You've probably used a REPL before and didn't even know it. The interactive ruby shell, otherwise known as IRB is the default REPL that ships with Ruby. It's also the same REPL you get when you run rails console. Read more...