[ruby-core:39822] Re: 2.0 feature questionnaire

2011/10/1 SASADA Koichi <[e-mail]>:
> I made a questionnaire "What do you want to introduce in 2.0?" in my
> RubyConf2011 presentation.
>
> Followings are results from my memo. =A0My memo should be incomplete, so
> please complement them.

Thank you for the list. I'd like to introduce:

1. Module#prepend. Include a module ahead of the ancestor chain.

2. Refinements. @shugo's proposal.

3. MVM, with inter-vm message passing.

4. Fast, native debugger. We have ruby-debug19, but it relies on
internal headers and API so it's hard to build and often broken.

5. Easy module dependencies and a hook for "included in a class."
Nesting modules to build up behavior could be friendlier and more
concise.

# Low-level included hook makes this possible, but not so pretty.
module A
  def self.included(klass) klass.class_eval { print 'A' } end
end

# Concise form:
module A
  class_included { print 'A' }
end


# Handling dependent modules is a headache if you want to
# call a hook on each dependent module when this is included
# in a class. It's worse if you nest dependent modules further.
# You have to handle the dependencies yourself in self.included
# or expect the class to include them also (by documenting the
# requirement, for example).
module B
  def self.included(klass)
    klass.class_eval { include A }
    print 'B'
  end
end

module C
  def self.included(klass)
    klass.class_eval { include B }
    print 'C'
  end
end

class Example
  include C
end

# prints ABC


# Much simpler
module B
  include A
  class_included { print 'B' }
end

module C
  include B
  class_included { print 'C' }
end

class Example
  include C
end

# prints ABC


See http://en.ihower.tw/post/454873995/rails3-activesupport-concern
for more on module dependencies and how ActiveSupport::Concern wraps
up these conventions.

Jeremy