Ruby 1.8.7：无法从自定义gem加载模块

Question

After creating a custom gem I'd like to reference functions defined in a module it contains.

Custom gem is dsi_core and the module lib/cuke.rb contains simply:

module DsiCore
    module Cuke
        def self.Features(*args)
            puts "Hello world!"
        end
    end
end

I've installed the gem and can see /var/lib/gems/1.8/gems/dsi_core-0.1.0/lib/cuke.rb exists as it should.

In another gem dsi_fabric there is the code dsi_fabric/lib/dsi_fabric :

require 'dsi_core'
# ...
DsiCore::Cuke.Features(*ARGV)

Trying to run this from the lib/ directory of dsi_fabric gem:

ruby -rubygems ./dsi_fabric.rb arg1 arg2

..results in:

./dsi_fabric.rb:7: uninitialized constant DsiCore::Cuke (NameError)

This refers to the Cuke.Features line in dsi_fabric.rb .

What am I doing wrong?

Answer 1

You're requiring 'dsi_core' instead of 'cuke'. Try changing require 'dsi_core' to require 'cuke' .

Answer 2

If you are testing in existing namespace problem can be namespace, so try with root namespace reference.

::DsiCore::Cuke.Features(*ARGS)

also like I mentioned in comment you need to put

def self.Features(*args)
  # ...
end

Hehe I do not like that capital method name annotation but to each his own :)

EDIT

Also try

require 'rubygems'
require 'dsi_core'

Answer 3

I was miscomprehending how Gem imports work.

If you create a gem and add other gem dependencies to it in the gemspec, those dependencies are automagically imported already.

Therefore what I have above is wrong - to import the cuke.rb file from gem dsi_core in gem dsi_fabric you would use:

require 'cuke'

ie the require dsi_core is implicit by nature of the Gem specification and gemspec.

Then to reference in the code would be

DsiCore::Cuke

..as I originally posted.

I was confused because mny public gems indicate you should use require with the form:

require `gem-name/module-or-class`.

However this is misleading: the gem name isn't being used at all, but rather a directory named after the gem:

require 'dir-name/module-or-class'

In this example the gem gem-name has the following directory structure:

lib/gem-name/module-or-class.rb

ie they've made a folder in the gem's lib/ directory named after the gem itself.