Ruby flew too

Understanding the guts of Ruby Version Management by rolling your own I've been tinkering with a fresh install of Ubuntu 12.10, setting up a nice clean development environment. One of the first things to do, of course, is implement some sort of Ruby version management. RVM and rbenv seem to be the clear winners in this arena, though there are a lot of tools out there that do a similar job . Writing your own version management for your Rubies isn't actually all that difficult. At it's core, we need need two things: A way to segregate the executables of the various versions A way to call the versions at will Segregating versions is trivial - working with files and folders, we can put the various versions into named directories. Actually executing our different versions is not all that difficult either. One way would be to create aliases with version numbers and explicitly call those when we want to use them. The more popular way, however, is to manipulate our PATH ...

What do you do when you love your spec testing with Capybara but you want to veer off the beaten path of Rspec and forge ahead into MiniTest waters? Follow along, and you'll have not one, but two working solutions. The setup Quickly now, let's throw together an app to test this out. I'm on rails 3.2.9. $ rails new minicap Edit the Gemfile to include a test and development block group :development, :test do gem 'capybara' gem 'database_cleaner' end Note the inclusion of database_cleaner as per the capybara documentation And bundle: $ bundle We will, of course, need something to test against, so for the sake of it, lets throw together a scaffold, migrate our database and prepare our test database all in one big lump. If you are unclear on any of this, go read the guides . $ rails g scaffold Book name:string author:string $ rake db:migrate $ rake db:test:prepare Make it minitest To make rails use minitest , we simply add a require ...

Reproducing the Elo rating algorithm in Ruby is a little challenge that I took upon myself recently for a small hack. The same Elo rating system that was scrawled upon the glass in "The Social Network" as the algorithm that Mark Zuckerberg used on rank people on FaceMash. As an exercise, here's a pass at it with a little BDD thrown in for good measure. A new file - elo.rb: require 'minitest/spec' require 'minitest/autorun' describe "result" do describe "when both players start with rating of 100 and k factor of 30" do it "must return 115 for the winner" do new_rating.must_equal 115 end end end Starting a new algorithm is always tricky. We know that the Elo rating system is essentially concerned with assigning ratings to players based on the outcome of their games or matches. In fact, it is widely used as a chess ranking algorithm. At a first glance then, I thought I might want to jump in and start mo...

Ruby has, at its root, an Object. Methods available in Object are available to every class because every class in Ruby inherits from Object somewhere in its own class hierarchy. Of course, you can override methods in subclasses, changing the functionality of a root method. You might stumble on to this idea if you work through Test Driven Development By Example by Kent Beck, translating the Java code into Ruby as you go. At some point pretty early on, he overrides the equality method on the Currency class to better test if two instances are equal. I'm going to do the same here, working with Instruments instead of Currency. Equality Equality in Ruby can be expressed using any of the following three methods object == other equal?(other) eql?(other) These methods are defined on the base Object. The default implementation of equality will only return true if both objects are exactly the same. The interesting thing is that although these three methods start out functioning the...

Rails has a lovely feature as part of ActiveRecord - Callbacks; to wit: Callbacks are hooks into the life cycle of an Active Record object that allow you to trigger logic before or after an alteration of the object state Basically, that means that you can instruct Rails to execute your own code throughout the process of creating, updating and destroying objects/records. You can, for example, use them to set some default values on create, or perhaps do some last minute validation, or even fire an event just after you've saved a record. The available callbacks are: after_initialize after_find after_touch before_validation after_validation before_save around_save after_save before_create around_create after_create before_update around_update after_update :before_destroy around_destroy after_destroy after_commit after_rollback At the same time, Ruby methods have the concept of implicit return values. That is to say, any method will return the value of the la...

If you work with Ruby on Windows in a corporate environment, sooner or later, you will hit an error when you are trying to install or update Gems. In my case, I simply had to set a few environment variables and I was good to go. RubyGems uses the HTTP_PROXY, HTTP_PROXY_USER and HTTP_PASS by default so if you open up a command prompt and set these as follows, it will use them to find the proxy and authenticate you to your proxy server: set HTTP_PROXY=http://pr.oxy.ip:port set HTTP_PROXY_USER=domain\user.name set HTTP_PASS=sUp3rS3curepAs$w0rd Extra points: A reader sent me a comment that this will only work when the proxy is using basic authentication. If you're having trouble using this method then you can give ntlmaps a shot. It's basically a little bit of python magic that sets up a proxy on your localhost through which you can route traffic and it will handle the authentication with your proxy server for you.

There are always times when you need to override the default RESTful routes in Rails. The most common case for this is mapping a /logout url to a session#destroy controller and action. However, this simple example doesn't really help when you want to achieve something a little more intricate - for example using a completely different url for a resource. Examples include a blog when you want your urls to add blog posts to be /add rather than blogs/new. Or what about a application with a Users model that has different types of users that can be added - perhaps it is a medical database and you have Doctors and Nurses - you want your urls to reflect the kind of person you are adding or editing - so doctor/new or nurse/new rather than users/new. Mapping urls like this is easy. However there is a little gotcha that you have to be aware of. Let's walk through an example and we'll see how to make it work New project We'll create a simple project for this example - a hypoth...