[ruby-core:85083] [Ruby trunk Feature#14394] Class.descendants

Issue #14394 has been updated by ridiculous (Ryan Buckley).


Thanks for the reply, shevegen, those are helpful questions :)

The gems I've seen implement this are active-support and dry-rb, with other people checking ObjectSpace to get the list (which can be very slow for large apps).

The most common use case for this that I've seen, is implementing the Chain of Responsibility pattern. In this case, we want to find a "handler" class for a certain type of input, from a list of registered classes. Instead of configuring the handlers as a static array, it's easier and more flexible to be able to lookup the list dynamically at runtime. The lookup is done by finding all subclasses of a certain base class. Because there is no fast and out-of-the-box way to do this, I've historically opted for the configured list approach. 

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Feature #14394: Class.descendants
https://bugs.ruby-lang.org/issues/14394#change-69798

* Author: ridiculous (Ryan Buckley)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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There have been numerous implementations of the method Class.descendants by various gems. However, I can't help but think that this ability should be included in the Ruby language itself. Especially since Ruby already offers the counterpart method Class.ancestors.

Would it possible to add a `descendants` class method?



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