How do I log correctly inside my Ruby gem?

Question

Currently I'm using puts, but I'm sure that's not the correct answer. How do I correctly setup a logger, inside my gem, to output my internal logging instead of puts?

Answer 1

The most flexible approach for users of your gem is to let them provide a logger rather than setting it up inside the gem. At its simplest this could be

class MyGem
  class << self
    attr_accessor :logger
  end
end

You then use MyGem.logger.info "hello" to log messages from your gem (you might want to wrap it in a utility method that tests whether a logger is set at all)

Users of your gem can then control where messages get logged to (a file, syslog, stdout, etc...)

Answer 2

You can keep the logger in your top-level module. Allow user's to set their own logger but provide a reasonable default for those who don't care to deal with logging. For e.g.

module MyGem
  class << self
    attr_writer :logger

    def logger
      @logger ||= Logger.new($stdout).tap do |log|
        log.progname = self.name
      end
    end
  end
end

Then, anywhere within your gem code you can access the logger. For e.g.

class MyGem::SomeClass

  def some_method
    # ...
    MyGem.logger.info 'some info'
  end

end

References:

• Using the Ruby Logger
• Logger