Ruby Gems with flexible gem dependencies?

Question

I'm about to extract major functionality of a larger project into a ruby gem.

The little framework I created uses a few additional gems, for different import/export options. Ie.

• FasterCSV (for ruby 1.8) for csv import/export
• Nokogiri for csv import/export
• GraphViz for graph ...
• PDF
• ...

I don't want users of the gem to install and load all the gems when they don't need them.

Is that possible at all?

Answer 1

The code in your initializer is just code... you could have your gem-user pass through a set of config options, and make the config.gem dependencies only load if those options are present. one way to do this would be to get them to set up global-values in config environemtn eg in config/environment.rb:

CSV_EXPORTS = XML_EXPORTS = true
PDF_EXPORTS = false

Then in your own gem, you'd write:

config.gem 'fastercsv' if defined?(CSV_EXPORTS)
config.gem 'nokogiri'  if defined?(XML_EXPORTS)
if defined?(PDF_EXPORTS)
  config.gem 'prawn' 
  config.gem 'prawn-layout'
end
# etc 

use "defined?" so that if they don't set up any at all, the gems won't try to load. It also means you can default them to whatever you like.