Ruby 2.1 In Detail
globaldev.co.uk
globaldev.co.uk
The page says:
> This is now no longer an issue, Ruby 2.1 uses a method cache based on the class hierarchy, invalidating the cache for only the class in question and any subclasses.
How does this work with an instance of a class? Does it invalidate only that instance's method cache, or all instances in that class? If I do DCI-style:
@user.extend(PasswordConfirmable)
That class is below `User` in the hierarchy:
class User; def foo; "foo"; end; end
# => :foo
module M; def bar; "bar"; end; end
# => :bar
u = User.new
# => #<User:0x007f2e1abc9e00>
u.extend M
# => #<User:0x007f2e1abc9e00>
u.singleton_class.ancestors
# => [#<Class:#<User:0x007f2e1abc9e00>>,
M,
User,
Object,
PP::ObjectMixin,
Kernel,
BasicObject]I'm curious as to whether the ruby-core team implemented method caches for every Object in the system (eg: every instance of User would then have its own method cache because they all would have their own singleton classes) or just objects that are instances of the Class class. I seem to doubt that the former happened because it seems like it would be expensive to maintain a cache for every object, that means a normal Rails request that generates 65,000 strings would all have their own method caches. Only instances of the Class class having their own method caches sounds more reasonable from a performance standpoint to me.
For what it's worth, I've been trying to get an answer about this from a ruby-core member, although my attempts have been quite lazy through Twitter.
The method cache works by invalidating anything below the class(es) whose methods have changed on the ancestor chain.
You're right that it can't be seen from user code, but if you take the implementers at their word about how it works, then this should be a perfectly convincing demonstration.
Or, if you don't believe me, read the source yourself:
https://github.com/ruby/ruby/blob/ba6b0acdb6c371f9f7150bed6f...
https://github.com/ruby/ruby/blob/1aa54bebaf274bc08e72f9ad38...
The part that clears the class hierarchy is here:
https://github.com/ruby/ruby/blob/1aa54bebaf274bc08e72f9ad38...
Alternatively, see Koichi's presentation at RubyKaiga:
Thanks to the Ruby team for all the hard work on 2.1, it looks like there's a lot of little changes in there.
$ ruby -v
ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin13.0]Specifically, I believe they're planning on breaking API compatibility within major version numbers.
Yes. Full details: https://www.ruby-lang.org/en/news/2013/12/21/semantic-versio...
> MINOR: increased every christmas, may be API incompatible
That is not semantic versioning.