Railscasts - Gem Dependencies

#110

May 23, 2008

Gem Dependencies

In Rails 2.1 we now have the ability to set gem dependencies. Now it's easier than ever to specify which ruby gems our rails app relies on.

Tags: rails-2.1 plugins tools

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Resources

# config/environment.rb
config.gem "RedCloth", :version => ">= 3.0.4", :source => "http://code.whytheluckystiff.net/"
config.gem 'aws-s3', :lib => 'aws/s3'

# config/environments/test.rb
config.gem 'mocha'
config.gem 'Shoulda'

rake -T gems
rake gems
rake gems:install
rake gems:unpack
rake gems:build
rake gems RAILS_ENV=test

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14 comments

1. Aditya Sanghi May 23, 2008 at 00:25

Hi Ryan,

Is it still the norm to change environment.rb or should we be doing this in the initializers?

Cheers,
Aditya

2. kino May 23, 2008 at 01:00

very useful stuff. 10nx

3. Henrik N May 23, 2008 at 03:01

Minor thing: you can do RAILS_ENV=test instead of RAILS_ENV='test'.

4. Ryan Bates May 23, 2008 at 07:08

@Aditya, anything that uses "config" I like to keep in the environment.rb. Anything that doesn't (where you can specify it after the config) then move that into an initializer.

@Henrik, yeah, my quote finger was a little twitchy last night it seems. ;)

5. Andrew Chalkley May 23, 2008 at 16:55

Another great rails cast!

Could you do some on ActionMailer?

6. Sebastian May 25, 2008 at 05:16

@Andrew - ActionMailer is good described in Agile Webdevelopment.

7. Jon Buda Jun 04, 2008 at 07:13

Ryan, as always great videos. Loved the 2.1 updates. I've recently been using config.gem and I think I found a problem using it with BlueCloth: http://railsforum.com/viewtopic.php?id=18850

Any idea whats going on here?

8. Faktura Jun 05, 2008 at 14:11

Greta video!

9. Mark Jun 23, 2008 at 08:36

Thanks for another great screencast. I just came across a gem's instructions to use:
:version => '~> 2.3.2'

What does ~> mean?

10. Mark Jun 23, 2008 at 08:52

Nevermind, there was an explanation:

gem 'mislav-will_paginate', '~>2.1'
# this will load any 2.x version
#(greater or equal to 2.1),
# but not 3.x

11. jan Jul 06, 2008 at 03:16

nice video :) thanks!

12. madan Aug 20, 2008 at 00:59

I am currently using mislav-will_paginate gem.
When I give it in environment.rb, it shows me 'mislav-will_paginate' file not found. I have given the proper version and source. Still it shows me the same error. How can I get rid of this error?

13. Matt Aug 29, 2008 at 11:50

I'd love to see how to make a gem plugin, similar to how you made a normal plugin in episode 33!

14. jhxc Sep 07, 2008 at 09:14

@madan, I had the same problem with a number of gems. It happens when the library module you're going to use is named differently from the gem. For example if you say

config.gem 'chardet'

=> rake can install the gem, but not unpack it, and rails gives the error

no such file to load -- chardet

and script/about gives the error

These gems that this application depends on are missing:
- chardet

To avoid this, you have to specify the name of the module:

config.gem 'chardet', :lib=>'UniversalDetector'