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author | Xavier Noria <fxn@hashref.com> | 2009-11-19 00:10:19 +0100 |
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committer | Xavier Noria <fxn@hashref.com> | 2009-11-19 00:10:19 +0100 |
commit | 2ddbef421cb877bc219ac2737bbba793c53edbde (patch) | |
tree | fab2bdf4739e53a4abfd13759c50f540190329aa /activesupport/lib/active_support/core_ext/object | |
parent | 5446d5cb05b50a9a3f317ded774be438e0eff909 (diff) | |
download | rails-2ddbef421cb877bc219ac2737bbba793c53edbde.tar.gz rails-2ddbef421cb877bc219ac2737bbba793c53edbde.tar.bz2 rails-2ddbef421cb877bc219ac2737bbba793c53edbde.zip |
explains the motivation for duplicable?
Diffstat (limited to 'activesupport/lib/active_support/core_ext/object')
-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. |