Problem requiring the RMagick gem with Ruby - ruby

Question

I installed RMagick on a Windows system with no apparent problems, but I'm having problems actually using it. In particular:
C:\Users\dancrumb> ruby -rubygems -rRMagick -e "puts Magick::Long_version"
C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:900:in `report_activate_error':
RubyGem version error: rmagick(2.12.0 not >= 0) (Gem::LoadError)
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:248:in `activate'
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:212:in `rescue in try_activate'
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:209:in `try_activate'
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:57:in `rescue in require'
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:35:in `require'
The main sticking block is the seemingly illogical error message: RubyGem version error: rmagick(2.12.0 not >= 0). Unless I'm missing something, 2.12.0 is most definitely greater than 0.
Some useful information:
C:\Users\dancrumb>gem environment
RubyGems Environment:
- RUBYGEMS VERSION: 1.6.2
- RUBY VERSION: 1.9.2 (2010-12-25 patchlevel 136) [i386-mingw32]
- INSTALLATION DIRECTORY: C:/Ruby192/lib/ruby/gems/1.9.1
- RUBY EXECUTABLE: C:/Ruby192/bin/ruby.exe
- EXECUTABLE DIRECTORY: C:/Ruby192/bin
- RUBYGEMS PLATFORMS:
- ruby
- x86-mingw32
- GEM PATHS:
- C:/Ruby192/lib/ruby/gems/1.9.1
- C:/Users/dancrumb/.gem/ruby/1.9.1
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- http://rubygems.org/
C:\Users\dancrumb>dir \Ruby192\lib\ruby\gems\1.9.1\gems
Volume in drive C is TI106036W0F
Volume Serial Number is 4432-A499
Directory of C:\Ruby192\lib\ruby\gems\1.9.1\gems
...
03/26/2011 01:34 PM <DIR> rmagick-2.12.0-x86-mswin32
...
03/20/2011 08:06 PM <DIR> rubygems-update-1.6.2
...
The supplied README file and the forums associated with RMagick don't afford any insight.
It gets weirder:
C:\Users\dancrumb>ruby -rubygems -e "gem 'rmagick', '2.12.0'; puts Magick::Long_
version"
C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:900:in `report_activate_error':
RubyGem version error: rmagick(2.12.0 not = 2.12.0) (Gem::LoadError)
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:248:in `activate'
from C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems.rb:1276:in `gem'
from -e:1:in `<main>'
As well as the specific question on RMagick, can anyone provide me with a sensible interpretation of the version error... it seems nuts to me, but maybe it is actually conveying something useful... just in a nutso way.

Answer 1

I had the very same problem in Ruby 1.8.7 as you with 1.9.1. This is a way I've resolved it:
Uninstall the rmagick gem if you have it (gem uninstall rmagick)
Download http://rubyforge.org/frs/download.php/64917/RMagick-2.12.0-ImageMagick-6.5.6-8-Q8.zip
Unpack the zip to separate folder (e.g. C:\temp\rmagick)
Install the ImageMagick-6.5.6-8-Q8-windows-dll.exe
Unpack the rmagick-2.12.0-x86-mswin32.gem to separate folder (e.g. C:\temp\rmagick\gem)
Extract the data.tar.gz to separate folder (e.g. C:\temp\rmagick\gem\data)
Open rmagick.gemspec and remove the line with s.platform = "mswin32"
Use "gem build rmagick.gemspec" to build the gem again (a "rmagick-2.12.0.gem" will be generated)
Use "gem install rmagick --local" to install it.

Answer 2

Type the following:
ruby --version
If its output is something like
ruby 1.9.2p180 (2011-02-18) [i386-mingw32]
it means the Ruby was built using mingw32, which was not supported by the RMagick.
Though README.html of RMagick-2.12.0-ImageMagick-6.5.6-8-Q8 package says
Ruby 1.8.6, installed via the One-Click Installer.
in the prerequisites, the latest One-Click Installer is built using mingw32, and that causes the trouble.

Answer 3

Looking at the source code for rubygems, it looks like rmagick might be responding incorrectly to rubygems' queries about its version for some reason; not sure what.
When you don't supply a specific version number, rubygems will fall back on >= 0 as its version_requirements.
Try this instead, to be more explicit, and so the versions match exactly:
ruby -rubygems -e "gem 'rmagick', '2.12.0'; puts Magick::Long_version"