Detect if a gem has been activated
A gem is activated if it is either in the current bundle (Gemfile.lock), or if you have manually activated it using
Kernel#gem
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(old-school).
To detect if e.g. activerecord has been activated:
if Gem.loaded_specs.has_key?('activerecord')
# ActiveRecord was activated
end
Detect if a particular gem version has been activated
To detect if e.g. activerecord matches a requirement like >= 3.2.0:
requirement = Gem::Requirement.new('>= 3.2.0')
version = Gem.loaded_specs['activerecord'].version
if requirement.satisfied_by?(version)
# ActiveRecord 3.2+ was activated
end
Detect if a gem has been required
Rails will automatically require all the gems in your Gemfile, unless you pass the require: false option. When working on non-Rails project (such as a gem), nothing is required automatically.
To detect if a gem has been required, use defined? on one of the modules defined by that gem:
if defined?(ActiveRecord)
puts 'ActiveRecord has already been required'
end
Note that defined? is a keyword (not a method) and will not crash while evaluating its argument.
Posted by Henning Koch to makandra dev (2016-09-27 09:34)