module Kernel
RubyGems adds the gem method to
allow activation of specific gem versions and overrides the require method
on Kernel to make gems appear as if they live on
the $LOAD_PATH
. See the documentation of these methods for
further detail.
Public Instance Methods
Private Instance Methods
Use #gem to activate a specific
version of gem_name
.
requirements
is a list of version requirements that the
specified gem must match, most commonly “= example.version.number”. See Gem::Requirement for how to specify a
version requirement.
If you will be activating the latest version of a gem, there is no need to call #gem, Kernel#require will do the right thing for you.
#gem returns true if the gem was activated, otherwise false. If the gem could not be found, didn't match the version requirements, or a different version was already activated, an exception will be raised.
#gem should be called before any require statements (otherwise RubyGems may load a conflicting library version).
#gem only loads prerelease versions
when prerelease requirements
are given:
gem 'rake', '>= 1.1.a', '< 2'
In older RubyGems versions, the environment variable GEM_SKIP could be used to skip activation of specified gems, for example to test out changes that haven't been installed yet. Now RubyGems defers to -I and the RUBYLIB environment variable to skip activation of a gem.
Example:
GEM_SKIP=libA:libB ruby -I../libA -I../libB ./mycode.rb
# File lib/rubygems/core_ext/kernel_gem.rb, line 43 def gem(gem_name, *requirements) # :doc: skip_list = (ENV['GEM_SKIP'] || "").split(/:/) raise Gem::LoadError, "skipping #{gem_name}" if skip_list.include? gem_name if gem_name.kind_of? Gem::Dependency unless Gem::Deprecate.skip warn "#{Gem.location_of_caller.join ':'}:Warning: Kernel.gem no longer " "accepts a Gem::Dependency object, please pass the name " "and requirements directly" end requirements = gem_name.requirement gem_name = gem_name.name end dep = Gem::Dependency.new(gem_name, *requirements) loaded = Gem.loaded_specs[gem_name] return false if loaded && dep.matches_spec?(loaded) spec = dep.to_spec Gem::LOADED_SPECS_MUTEX.synchronize { spec.activate } if spec end