Contents

#--
# Uninheritable
#
# Copyright (c) 2003 Austin Ziegler
#
# Ruby License
#
# This module is free software. You may use, modify, and/or redistribute this
# software under the same terms as Ruby.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.
#
# ==========================================================================
#  Revision History
# ==========================================================================
#
#  2003.9.17  Austin Ziegler
#    - Minor modifications to documentation.
#
# ==========================================================================
#++

#:title: Uninheritable
#
# Allows an object to declare itself as unable to be subclassed. The
# technique behind this is very simple (redefinition of #inherited), so this
# just provides an easier way to do the same thing with a consistent error
# message.
#
# == Usage
#
#   require 'calibre/uninheritable'
#
#   class A
#     extend Uninheritable
#   end
#
#   class B < A; end # => raises TypeError
#
# == Author(s)
#
# * Austin Ziegler
#

module Uninheritable
  # Redefines a class's #inherited definition to prevent subclassing of the
  # class extended by this module.
  def inherited(klass)
    raise TypeError, "Class #{self} cannot be subclassed."
  end
end



#  _____         _
# |_   _|__  ___| |_
#   | |/ _ \/ __| __|
#   | |  __/\__ \ |_
#   |_|\___||___/\__|
#

=begin testing

require 'test/unit'

class TC_Uninheritable < Test::Unit::TestCase

  class Cannot
    extend Uninheritable
  end

  class Can
  end

  def test_module
    assert_nothing_raised {
      self.instance_eval <<-EOS
        class A < Can; end
      EOS
    }
    assert_raises(TypeError, "Class Cannot cannot be subclassed.") do
      self.instance_eval <<-EOS
        class B < Cannot; end
      EOS
    end
  end

end

=end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
facets-1.0.3	packages/more/lib/facet/uninheritable.rb