How to make constants really 'private'

00_README.md

How to make constants really 'private'

There's a constant misunderstanding about how private method works...

For example, this DOES NOT make BAR a private constant:

class This
  private
  BAR = 'bar'.freeze
end

puts This::Bar
# => bar

Then how??

Module#private_constant to the rescue

class This
  BAR = 'bar'.freeze
  private_constant :BAR
end

puts This::Bar
# displaying error
# private_c.rb:16 in `<main>': private constant This::Bar reference error
# shell returned 1

This works with any constant, including classes and modules:

# frozen_string_literal: true

class This
  class Other
    class << self
      def foo
        'x'
      end
    end
  end
  private_constant :Other

  def access
    puts Other.foo
  end
end

This.new.access  # Will be ok..
# And this will error
This::Other.foo

Thanks for watching!!

01_not_really_private_constant.rb

# frozen_string_literal: true

class This
  private
  BAR = 'bar'.freeze
end

puts This::Bar
# => bar

02_private_constant.rb

# frozen_string_literal: true

class This
  BAR = 'bar'.freeze
  private_constant :BAR
end

puts This::Bar
# displaying error
# private_c.rb:16 in `<main>': private constant This::Bar reference error
# shell returned 1

03_private_constant_with_classes.rb

# frozen_string_literal: true

# Module#private_constant in action
# It works with any constant, including classes and modules
class This
  class Other
    class << self
      def foo
        'x'
      end
    end
  end
  private_constant :Other

  def access
    puts Other.foo
  end
end

This.new.access  # Will be ok..
# And this will error
This::Other.foo