I am sure you have done this. You find a railscast about something you are interested in, and besides watching the vid, you want to run the app.

You download it, and all heck breaks loose due to the rc demo using older versions of just about anything. Rather than using RVM or something to create or duplicate the original environment, I prefer just to upgrade it to the most current thing I am using on my dev machine. I really don’t like loading up old versions of stuff all over the place.

One issue i ran into..some weird issue about a configuration file. Differences in configuration can happen with major upgrades, say going from rails 3.2 to 4.x.

Rails provides a rake rails:update task to update configuration files. Be sure you’ve committed your application with git before running rake rails:update in case you need to roll back changes.

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def update_config_files
puts "rake rails:update"
end

The rake rails:update will identify every configuration file in your application that differs from a new Rails application. When it detects a conflict, it will offer to overwrite your file.

Don’t blindly allow rake rails:update to overwrite your files. Many of your files will be different because you’ve made changes from a default new Rails application. You’ll need to check each file to determine if rake rails:update is seeing your own changes or pointing out changes due to a Rails update.

When rake rails:update offers to overwrite a file, enter d (for “diff”) and review the differences. Most differences will be your own. If you’re uncertain, don’t overwrite the file; make a note for yourself and investigate later. If you are certain that the difference is due to a Rails version change, you can allow rake rails:update to overwrite the file.