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17.3 Brand-new engine
Brand-new engine
The layout of an engine is nearly identical to that of
a Rails application, with the notable exception that
all code that usually goes straight into the app directory
now goes into a namespace. Let’s take a look at
the layout of the forem engine 10 at an early stage of
its development, shown in figure 17.1.
You’re going duplicate a little chunk of this code
using the same practices that were used to develop
forem. It’s a good an example as any. 11
17.3.1 Creating an engine
Here you’ll create your engine using a generator
built-in to Rails.
WARNING You’re going to need to use
at least the Rails 3.1 version for this,
which is what you should have installed
from earlier chapters in this book.
You can run this executable file to generate the layout
of your engine using this command at the root
of the Ticketee application you created earlier:
cd ..
rails plugin new forem --mountable
The --mountable option here is the magic incantation:
it tells the plugin generator that you want to
generate a mountable plugin, more commonly known as an engine. The output of this
command is very similar to that of an application, containing an app directory and a
config/routes.rb file. But that’s what an engine is essentially: a miniature application!
This command even runs bundle install automatically for you on this new engine,
like the rails new command does when you generate a new application.
Before you go any further, run bundle --binstubs in this new directory so that
you can use bin/rspec to run your tests, rather than bin/rspec.
Before you get too involved here, you’re going to set this project up as a Git repository
and create a base commit that you can revert back to if anything goes wrong.
You’ll first need to change back into the forem directory, then set up the git repository:
git init
git add .
git commit -m "Initial base for the forem engine"
10 http://github.com/radar/forem.
11 It also helps that one of the authors of this book has done extensive work on it.
Figure 17.1 The forem engine,
directory structure
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