duplicable.rb

Path: lib/active_support/core_ext/object/duplicable.rb
Last Update: Tue Feb 05 05:43:31 -0500 2013

Most objects are cloneable, but not all. For example you can‘t dup nil:

  nil.dup # => TypeError: can't dup NilClass

Classes may signal their instances are not duplicable removing dup/clone or raising exceptions from them. So, to dup an arbitrary object you normally use an optimistic approach and are ready to catch an exception, say:

  arbitrary_object.dup rescue object

Rails dups objects in a few critical spots where they are not that arbitrary. That rescue is very expensive (like 40 times slower than a predicate), and it is often triggered.

That‘s why we hardcode the following cases and check duplicable? instead of using that rescue idiom.

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