Posted by
arungupta on September 4, 2007 at 11:09 AM PDT
As a newbie to
Rails, "Gem" and "Plugin" terminology
was slightly confusing to me. Specifically I saw the terms being used
interchangeably sometimes. This
TOTD highlights the
difference between Ruby Gem and
Rails Plugin.
Ruby Gem and Plugin are both packaging systems - the main difference is the
scope in which they are effective. The common differences are highlighted in the table
below.
| Topic |
Ruby Gem |
Rails Plugin |
| Definition |
A Gem is a packaged Ruby application using the packaging
system defined by RubyGems. |
A Rails plugin is a
packaged Ruby application that extends the core
Rails framework. |
| Example |
Has a
name (e.g. rake) and a version (e.g. 0.4.16).
Rails is also installed as a Gem. |
Has a name (e.g.
Goldspike)
and a version (e.g. 1.1.1). |
| Scope |
Installed in the Ruby or JRuby installation
and is available to all applications run using that interpreter. |
Installed in a specific Rails app only. |
| Packaging System |
Rails gem is installed in
jruby-1.0\lib\ruby\gems\1.8\gems\rails-1.2.3 as:<DIR>
bin
<DIR> builtin
68,465 CHANGELOG
<DIR> configs
<DIR> dispatches
<DIR> doc
<DIR> environments
307 fresh_rakefile
<DIR> helpers
<DIR> html
<DIR> lib
1,072 MIT-LICENSE
11,969 Rakefile
8,001 README
The lib directory contains all the gem source code. |
Goldspike plugin is installed in
vendor\plugins\rails-integration directory of the application as:
7,089 build.xml
1,141 LICENSE.txt
<DIR> plugins
6,675 pom.xml
1,447 README
<DIR> samples
plugins/goldspike directory consists of
24 init.rb
25 install.rb
<DIR> lib
549 Rakefile
536 README
<DIR> tasks
<DIR> test
The lib directory contains all the plugin source code. |
| Management |
Gems are managed on your computer using the gem command. You can install, remove and query gem
packages using the gem command. |
Plugins can be installed using after creating a Rails application and then
invoking the command
ruby script\plugin install [url or name of plugin] |
| Load Path |
gem command adds the lib
directory of your gem to the load path of Ruby. |
Rails adds the lib directory of plugin in
your application's load path. |
| Specific Features |
|
- Bundled Rake tasks that get automatically loaded into your
Rakefile
- An installation hook (install.rb)
- An application initialization hook for the plugin to inject
itself (init.rb)
- ability to bundle additional generators (for the
script/generate script)
|
| Publish Format |
A Gem may be published as Plugin, for
example ActiveRecord-JDBC. |
A Plugin cannot be published as Gem. |
Here are some useful entries (with numerous pointers on screencasts, blogs,
tips & extensive feature sets) to get you started with JRuby:
Are there any other main differences that I missed ?
Please leave suggestions on other TOTD that you'd like to see. A complete
archive is available here.
Technorati:
totd
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