I’ve had to interview hundreds and learned a lot of lessons. With that, here’s my best advice to anyone else who wants hire a Rails developer:
Don’t hire someone that doesn’t know Rails at all. Perhaps as with all things, you want to hire someone who has self-selected to do that job. Rails is famously easy to get started with you can literally be running your first Rails app minutes after visiting rubyonrails.org for the first time. I won’t hire anyone who hasn’t at least built and deployed a couple of projects in their spare time and who understands both the advantages and disadvantages of using the technology.
A personal Rails blog is required. Every Rails developer should have a blog to engage with the community. On a related note, I’ve often asked candidates to list their favorite Rails blogs or even show me their newsreader. They should know most of the top Rails blogs and who’s behind them.
Be wary of holes in proficiency. Rails developers should be fearless. Its reasonable to expect them to have a command of everything from database indices to cross-platform JavaScript. (Bonus points if they are handy in Photoshop and Illustrator.)
If they are using Mephisto or Typo then they’ve been exposed to an established rails code base and have successfully deployed it and even customized it.
As my company does social media software, engaging in the blogosphere is good experience. How else can you really learn the nuances of FeedBurner and Technorati, etc., if you haven’t had a blog?
Lastly there’s the psychological effect of identifying yourself publicly as a Rails developer. That’s a commitment, and addresses my Tip #3 about finding candidates that have self-selected to do Rails.
If you’re a half decent Rails programmer, with an app in the real world, the nature of the framework forces you NOT to have any holes in proficiency. I started as a Designer (so I agree with the no CS degree!) and before Rails I knew nothing about sysadmin and little of javascript but Rails forces (and helps) you to learn every part of web development.
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