Rails%203%20In%20Action

512 CHAPTER 17 Engines
17.8 Releasing as a gem
By releasing your engine as a gem, you’ll make it publicly available for anybody to
download from http://rubygems.org. This will also allow you to share this engine
across multiple applications. If people wish to use your engine, they would be able to
put this line in their Gemfile of their application:
gem 'forem'
Then they would need to go about configuring the application to have a config/initializers/
forem.rb file with the proper configuration options (only Forem::Engine.user_class for
now, but possibly others). You’d usually put these steps in a README file at the root of
the engine. 22
To release your engine as a gem, you can use Bundler. Bundler provides some
gem-management tasks in the form of Rake tasks that allow you to build your gem
(basically, zip it up into a .gem file), 23 install the gem locally, and release it.
To make these tasks available for your engine, you can put this line at the bottom
of your Rakefile:
Bundler::GemHelper.install_tasks
When you run rake -T, you’ll see that you’ve got a few tasks for your engine, some of
which you’ve already used. This line that you’ve put in the Rakefile will add the build,
install, and release rake tasks.
Before you can release your gem, you must give it a unique name. To do this, you’ll
go into your application and rename forem.gemspec to your-name-forem.gemspec 24 to
make it unique. Then inside this file, you’ll need to change this line
s.name = "forem"
to have the same name as the gemspec:
s.name = "your-name-forem"
Now you’re ready to release your gem. Let’s run the rake build task first and see what
does:
(in /Users/ryanbigg/Sites/book/forem)
your-name-forem 0.0.1 built to pkg/your-name-forem-0.0.1.gem
This command has built your gem and put it in a new directory called pkg. This new
gem can be installed using gem install pkg/your-name-forem-0.0.1 if you wish, but
there’s a problem: this gem doesn’t contain all your files.
At the moment, the gem only contains the files specified by this line in your-nameforem.gemspec:
22 This is so when you put it in GitHub, people will have a clear way of seeing what this engine’s good for and
how they can use it.
23 Yup, .gem files are actually .zip files.
24 A wise decision here would be to use your GitHub username, as that’s bound to be unique, compared to your
first name which is most likely not.