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94 CHAPTER 4 Oh CRUD!
Figure 4.1 ActiveRecord::RecordNotFound exception
The ActiveRecord::RecordNotFound exception is Rails’ way of displaying exceptions
in development mode. Underneath this error, more information is displayed, such as
the backtrace of the error.
If you were running in the production environment, you would see a different error.
Stop the server that is currently running, and run these commands to start in production
mode:
rake db:migrate RAILS_ENV=production
rails server -e production
Here you must specify the RAILS_ENV environment variable to tell Rails you want to
migrate your production database. By default in Rails, the development and production
databases are kept separate so you don’t make the mistake of working with production
data and deleting something you shouldn’t. This problem is also solved by
placing the production version of the code on a different server from the one you’re
developing on. You only have to run the migration command when migrations need
to be run, not every time you need to start your server.
You also pass the -e production option to the rails server command, which
tells it to use the production environment. Next, navigate to http://[our-localip]:3000/project/not-here,
where [our-local-ip] is whatever the IP of your computer is
on the local network, like 10.0.0.2 or 192.168.0.3. When you do this, you get the standard
Rails 404 page (see figure 4.2), which, to your users, is unhelpful.
It’s not the page that’s gone missing, but rather the resource you’re looking for isn’t
found. If users see this error, they’ll probably have to click the Back button and then
refresh the page. You could give users a much better experience by dealing with the
error message yourself and redirecting them back to the home page.
To do so, you capture the exception and, rather than letting Rails render a 404
page, you redirect the user to the index action with an error message. To test that
users are shown an error message rather than a “Page does not exist” error, you’ll
write an RSpec controller test rather than a Cucumber feature, because viewing projects
that aren’t there is something a users can do, but not something they should do.
Plus, it’s easier.
Figure 4.2 “Page does not exist” error