From: "byroot (Jean Boussier)" Date: 2022-01-24T08:26:41+00:00 Subject: [ruby-core:107247] [Ruby master Feature#18273] Class#subclasses Issue #18273 has been updated by byroot (Jean Boussier). > In my view, this method does not play well with object lifetime, semantically. This is perfectly fine, Ruby isn't concerned about wether a `Class` is still present in the constant table or not (or if it ever was). That's also how the old Active Support implementation based on `ObjectSpace.each_object` behaved. That's why [`DescendantTracker` keeps a `WeakMap` of the unregistered classes to give the illusion in reload mode](https://github.com/rails/rails/blob/9062d705ad9055c0f3ec73505150e0e94fff5925/activesupport/lib/active_support/descendants_tracker.rb#L26). > If GC kicks in between lines 3 and 4, you may get different results. In my opinion, this non-determinism is not good for an API like this one. That too was considered and is fine. ---------------------------------------- Feature #18273: Class#subclasses https://bugs.ruby-lang.org/issues/18273#change-96108 * Author: byroot (Jean Boussier) * Status: Closed * Priority: Normal ---------------------------------------- Ref: https://github.com/rails/rails/pull/43481 Something we forgot to mention in [Feature #14394], is either a parameter or another method to only get direct descendants. Active Support has been offering `Class.subclasses` as: ```ruby def subclasses descendants.select { |descendant| descendant.superclass == self } end ``` It seems a bit silly to grab all descendants and then restrict the list when `Class#descendants` had to do some recursion to get them all in the first place. ### Proposal We could either implement `Class#subclasses` directly, or accept a parameter in `Class#descendants`, e.g. `descendants(immediate = false)`. cc @eregon -- https://bugs.ruby-lang.org/ Unsubscribe: