NameError: uninitialized constant error

Question

Given the following code:

module Backup
  module Destination
    class Base
      def initialize
        puts 'Base'
      end
    end
  end
end

module Backup
  module Destination
    class Test < Base
      def initialize
        puts 'Test'
        super
      end
    end
  end
end

Backup::Destination::Test.new

This works as expected, outputting:

Test
Base

However if I split things up like this:

# lib/backup.rb
require_relative 'backup/destination/base'

module Backup; end


# lib/backup/destination/base.rb
require_relative 'test'

module Backup
  module Destination
    class Base
      def initialize
        puts 'Base'
      end
    end
  end
end


# lib/backup/destination/test.rb
module Backup
  module Destination
    class Test < Base
      def initialize
        puts 'Test'
        super
      end
    end
  end
end

And execute with the following (from irb):

require_relative 'lib/backup'

I get this error:

NameError: uninitialized constant Backup::Destination::Base
    from /lib/backup/destination/test.rb:3:in `<module:Destination>'
    from /lib/backup/destination/test.rb:2:in `<module:Backup>'
    from /lib/backup/destination/test.rb:1:in `<top (required)>'
    from /lib/backup/destination/base.rb:1:in `require_relative'
    from /lib/backup/destination/base.rb:1:in `<top (required)>'
    from /lib/backup.rb:1:in `require_relative'
    from /lib/backup.rb:1:in `<top (required)>'
    from (irb):1:in `require_relative'

What am I missing?

Note: I couldn't post the above without adding more details. Stupid feature because in this case code is worth a thousand words. (this text allowed the question to be posted)

Answer 1

The problem is that you are requiring test.rb before your Base class is defined. One possible solution is to move your require to the bottom of base.rb .

Another possible solution is to remove your require from base and require both files in the correct order from backup .

Answer 2

Made the following changes to fix the problem:

# lib/backup.rb
require_relative 'backup/destination/base'
require_relative 'backup/destination/test'

module Backup; end

And removed the require_relative statement from lib/backup/destination/base.rb . This fixed the order of the require_relative statements. I mistakenly thought the files were required before anything was executed.