Question

I have a library of functions that is packaged up as a gem. One of these functions requires the use of a third-party gem that itself has a long list of dependencies.

Is there a way that I can set up my gem so that users can install it and use those functions in the gem that don’t have the third-party dependency without the runtime complaining?

I want an exception to be raised when the method with the dependency is called, but the user should be able to use the other functions without a runtime error.

Is this possible?

Answer 1

You can split your functions to modules (maybe modules to files too) that are depending or not depending gem. including GemDependent module trying to require your gem if not then redefine all gem dependent functions to raise exception.

module YourFunctions
  module GemDependent

    def self.included(klass)
      require "yourgem"
    rescue LoadError
      instance_methods.each do |m|
        define_method(m) { raise "you need yourgem to run #{m}" }
      end
    end

    def gem_dependent_function
    end
  end

  include GemDependent

  def no_dependent_function
  end
end

include YourFunctions
gem_dependent_function
#  "you need yourgem to run gem_dependent_function"