Category: ruby

Rails Migration Antipatterns and How To Fix Them

Migrations are one of the best features of Rails. Although some folks prefer pure SQL rather than Rails migration DSL, I don’t know of anyone who dislikes the idea of a versioned schema that can evolve in a controlled and repeatable fashion.

But because the concept of database migrations is such a powerful one, it’s tempting to jam any old change that affects the database into a new migration and run rake db:migrate to make it happen. I’ve been guilty of a bit of this in the past, and I’ve joined some projects that did other ugly things in migrations. In the process I’ve learned the hard way that there are some things you must never do in a migration or they will come back to haunt you later. Here they are.
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Making Bundler 0.8.5 install Nokogiri on Leopard with a newish libxml

Nokogiri on a standard installation of Leopard is complain-y about a couple of old libraries:

“HI. You’re using libxml2 version 2.6.16 which is over 4 years old and has plenty of bugs. We suggest that for maximum HTML/XML parsing pleasure, you upgrade your version of libxml2 and re-install nokogiri. If you like using libxml2 version 2.6.16, but don’t like this warning, please define the constant I_KNOW_I_AM_USING_AN_OLD_AND_BUGGY_VERSION_OF_LIBXML2 before requring nokogiri.”

Aaron Kalin figured out how to fix this if you’re installing nokogiri as a system gem, but I want to use Bundler and keep my system gems down to the bare minimum. I figured out how to do this under Bundler 0.8.5.
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Using RVM to install REE 1.8.7-2009.10

I’m trying out Ruby Version Manager this week, and my first impression is that this is some cool technology. But I wasn’t able to figure out how to get it to install an older version of REE to get around this bug (the “Marshal.load reentered at marshal_load” issue).

Igor P’s solution is correct (just install REE 1.8.7-2009.10), but it took a little fiddling to figure out how to get RVM to use the older version of REE. Here’s how to do it:

Fancier Stubbing of GeoKit for Rails unit tests

I’m working on a Rails app that uses the ym4r_gm plugin, getting Google to do the geocoding for Thentic. I liked the idea of stubbing the web service call, because all those calls to an external service add up to over 20 seconds of test suite run time(!). That’s almost half of the 50 second run time of my unit tests (and 50 seconds is much too long for a unit test suite).

I found a good starting point at geokit stubbing for faster tests. I also wanted a way to stub a geocoding failure, and a way to prevent any unit tests from using the real geocoding web service.

Here’s how I did it.
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Things I had to fix for Rails 2.2.2

The new features in Ruby on Rails 2.2.2 have been well documented, and I’m looking forward to using several of them on WhatYouAte.com. If you’re reading this you probably are too.

However, if you’re upgrading an existing project and you’re sticking with official releases (as opposed to edge Rails) like I am, your code probably needs some tweaking to work with Rails 2.2.2. Mine certainly did. Although there were a lot of failed tests with ugly stacktraces, there were only a few API changes in Rails that needed to be accomodated to fix them all. Here’s a list of the changes that broke my app, and what I had to do to get it working again.
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