Freezing Gems

What is a gem and why would you want to freeze it?

In Ruby, there are times when you want to access pieces of functionality that other people of written (3rd party libraries) and you normally have 2 options. You can install a plug in or install a gem. Normally the method you use is determined by which ever is made available by the author.

Gems are installed on the host machine and are pretty handy when you want to run things in the command line or else across lots of projects, but their downside is that if you use a gem in a Rails project there is no automatic publishing mechanism when you deploy your site. You will need to log onto the remote host machine and install the gem manually.

Plugins are specific to Rails and are similar to gems in that they are also 3rd party libraries. However they are associated with your Rails project as opposed to your machine so they will get posted to the server on a regular deploy.

Freezing a gem is the process of transforming a gem into a plug in. Essentially the gem is "unwrapped" and installed into your Rails plug ins directory.

1. Make sure the gem you want to freeze is installed.
   
2. Navigate to your Rails project's home directory and type the following
   
3. script/plugin install http://svn.ardes.com/rails_plugins/gems
   (this is the plugin which will freeze the gem)
   
4. rake gems:freeze GEM=gem_name

Note that not every gem can be frozen successfully. Some gems rely on executables which are platform specific and these cannot be accessed from the plugins directory.