Alex Le’s Blog

I’ve just released ActiveFixture, an enhancement to the Rails db:fixtures:load rake task. Currently db:fixtures:load doesn’t take into account the foreign key constraints hence with any tables that have foreign keys defined, db:fixtures:load would just fail miserably. As Rails is increasingly getting more into the enterprise world, the ability to handle foreign key correctly becomes more important.

I flew to New York last weekend for the VSLive! Conference. While attending VSLive! talks during the day, my mind was mostly occupied with how to solve this foreign key issue at night. After 2 days and trying multiple ways and still unable to solve the problem, I suddenly remembered about graph (good old CS classes). I turned the problem of determining the order of loading fixtures files into a graph problem of how to traverse the graph in a certain order. Breadth-first-search doesn’t give the correct answer, Depth-first-search seems to have some potentials. When I tried Depth-first-search Post order traversal, suddenly I realized that DFS post order gives the perfect solution. What’s even more beautiful is the entire traversal algorithm was only a couple lines of Ruby code as you can see from the source.

I’ve learned quite a bit about Rails and Ruby while writing ActiveFixture. I poked around the core ActiveRecord classes and see how fixture is being handled, I then learned how to use reflection to get meta data from the ActiveRecord models, then how to write rake task and componentize everything into a plugin. In the end, I feel I like working with Ruby and Rails even more. .NET is cool but somehow, to me, Ruby is more fun to work with, except for the fact that there’s no GUI debugger. I would say I would have been able to write ActiveFixture in much less amount of time had I had a Rails/Ruby IDE with an interactive debugger.

The next time I write something for Rails, I would probably give Ruby in Steel a shot. It’s quite frustrated when you are exploring Ruby, especially when someone like me isn’t that familiar with Ruby. I love the Watch and Intermediate Window in Visual Studio simply because I can hit a breakpoint and examine the application and all the variables at that moment. Currently we don’t have anything similar for Ruby and Rails for free. Ruby in Steel seems to have potentials, but $199 is quite a barrier to entry to any ruby-rails-fan. In fact, one of the main question that my boss at work asked me about Ruby on Rails, is if Ruby has any good IDE. My company is a Microsoft shop so we use Visual Studio extensively. It’s hard to convince someone who code in Visual Studio for a living to switch to a notepad-like editor (”no Intellisense, no thanks”) and start learning Ruby on Rails. Personally I use (and pay for) e-editor, however, I do miss the intellisense and the ability to hit F5 anytime to kill that freaking bug…Okay, enough of my ranting.

Anyway, here’s the good news in short: ActiveFixture is released and ready for abused. Current version is under-tested (I haven’t written any unit tests yet) and may contain bugs. For Wars of Earth, I have about 20 tables with a whole bunch of foreign key constraints (with circular references too) so I’m quite confident that ActiveFixture will work for you.

Download:

• SVN: http://activefixture.rubyforge.org/svn/

Install:

• Copy into the RAILS_ROOT/vendors/plugins
• As always, RTFM. See README for more information. I wrote a little explanation on how ActiveFixture works so enjoy It’s a nice and elegant algorithm to solve a tricky problem.

Usage:

• Make sure you have all the required yml/yaml/csv files
• Defined all belongs_to relationships inside your models
• Run

And Support:
Please vote for ActiveFixture to get included in Rails core. I’ll have even more incentives to write even more useful Rails plugins.

keywords spam: db:fixtures:load, db:fixtures:activeload, rails foreign key constraints fixtures, fixtures loading order

Tags: foreign keys, migration, Ruby on Rails