diff options
Diffstat (limited to 'activesupport/lib')
| -rw-r--r-- | activesupport/lib/active_support/core_ext/object/duplicable.rb | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb index a2d4d50076..b05325790c 100644 --- a/activesupport/lib/active_support/core_ext/object/duplicable.rb +++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb @@ -1,3 +1,19 @@ +# 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. class Object # Can you safely .dup this object? # False for nil, false, true, symbols, numbers, class and module objects; true otherwise. |