Test driven Clojure part III

October 03, 2012

Now that we have Leiningen installed we can start installing the rest of our Clojure toolkit and writing some code.

Creating the project.clj

We’ve come to our first major hurdle, what are we going to name this application? It needs to be catchy, easy to remember, and have great SEO potential. Lets go with “Katchie”! I can already start to see the money flowing in.

In your normal coding directory, lets create a folder where all of our code is going to live.

$ cd ~/Code
$ mkdir katchie
$ cd katchie

Following proper coding habits we’re going to create a project.clj. The project.clj stores the meta-information about a Clojure application. Here is where we’ll list our external dependencies and configure our setup.

(defproject katchie "0.0.1"
  :description "A socail news aggregator"
  :dependencies [[org.clojure/clojure "1.4.0"]
                 [joodo "0.11.0"]
                 [hyperion "3.3.0"]]
  :profiles {:dev {:dependencies [[speclj "2.3.1"]]}}
  :plugins [[speclj "2.3.1"]
            [joodo/lein-joodo "0.11.0"]]
  :test-paths ["spec/"]
  :java-source-paths ["src/"])

This might look complceted at first but lets break it down line by line.

(defproject katchie "0.0.1"

At the top level of our project.clj we call this special method defproject. The first argument is what we want to call the namespace of the project, and the second is a string representation of the version. We’re going to use “0.0.1” for now, until we add some features. But the end of this series we should be at our “1.0.0” release.

:description "A social news aggregator"

This is not very important to us, but if we were creating a tool for other developers to use, this would be the description they would see in leiningen next to the name of our project.

:dependencies [[org.clojure/clojure "1.4.0"]
               [joodo "0.11.0"]
               [hyperion "3.3.0"]]

These are the current dependencies of our project. We’ll be using Clojure version “1.4.0”, Joodo “0.11.0”, and Hyperion “3.3.0”. These might not be the current versions of these projects, but thats what we’ll use during the development of this project. After completing this series I’ll leave it as a task to you to update these libraries to their most recent versions then update the project to work the updated APIs.

:profiles {:dev {:dependencies [[speclj "2.3.1"]]}}

We have another dependency, and that our testing framework Speclj. We treat Speclj differently, because its a development dependency. We won’t need Speclj on our production server.

:plugins [[speclj "2.3.1"]
          [joodo/lein-joodo "0.11.0"]]

These lines add the Speclj and Joodo plugins to the Leiningen. Command line interface. We’ll be using their commands later in the series.

:test-paths ["spec/"]
:java-source-paths ["src/"])

These last lines help point our dependencies to the right locations.

That’s it for now. Running lein deps should spew out a bunch of output as it installs our dependencies. If this is the first time your installing Clojure, this might take a while.