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author | paulccarey <paulccarey@gmail.com> | 2010-07-29 15:34:59 +0100 |
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committer | paulccarey <paulccarey@gmail.com> | 2010-07-29 15:34:59 +0100 |
commit | 2b2ee222f3012a29c9db95d357a30029100b226b (patch) | |
tree | 6359b3994e1b4d77311c2fa039e0a7e9397357c8 /activesupport/lib/active_support/core_ext/class/attribute.rb | |
parent | c178a26ec784f34e82f08e26064d9798edb09e72 (diff) | |
parent | 873c5a9e5924a7776692b9a17b03d0becec6e513 (diff) | |
download | rails-2b2ee222f3012a29c9db95d357a30029100b226b.tar.gz rails-2b2ee222f3012a29c9db95d357a30029100b226b.tar.bz2 rails-2b2ee222f3012a29c9db95d357a30029100b226b.zip |
Merge branch 'master' of github.com:lifo/docrails
Diffstat (limited to 'activesupport/lib/active_support/core_ext/class/attribute.rb')
-rw-r--r-- | activesupport/lib/active_support/core_ext/class/attribute.rb | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb index 576366e496..bfa57fe1f7 100644 --- a/activesupport/lib/active_support/core_ext/class/attribute.rb +++ b/activesupport/lib/active_support/core_ext/class/attribute.rb @@ -2,8 +2,8 @@ require 'active_support/core_ext/kernel/singleton_class' require 'active_support/core_ext/module/remove_method' class Class - # Declare a class-level attribute whose value is inheritable and - # overwritable by subclasses: + # Declare a class-level attribute whose value is inheritable by subclasses. + # Subclasses can change their own value and it will not impact parent class. # # class Base # class_attribute :setting @@ -18,12 +18,34 @@ class Class # Subclass.setting # => false # Base.setting # => true # + # In the above case as long as Subclass does not assign a value to setting + # by performing <tt>Subclass.setting = _something_ </tt>, <tt>Subclass.setting</tt> + # would read value assigned to parent class. Once Subclass assigns a value then + # the value assigned by Subclass would be returned. + # # This matches normal Ruby method inheritance: think of writing an attribute - # on a subclass as overriding the reader method. + # on a subclass as overriding the reader method. However, you need to be aware + # when using +class_attribute+ with mutable structures as +Array+ or +Hash+. + # In such cases, you don't want to do changes in places but use setters: + # + # Base.setting = [] + # Base.setting #=> [] + # Subclass.setting #=> [] + # + # # Appending in child changes both parent and child because it is the same object: + # Subclass.setting << :foo + # Base.setting #=> [:foo] + # Subclass.setting #=> [:foo] + # + # # Use setters to not propagate changes: + # Base.setting = [] + # Subclass.setting += [:foo] + # Base.setting #=> [] + # Subclass.setting #=> [:foo] # # For convenience, a query method is defined as well: # - # Subclass.setting? # => false + # Subclass.setting? # => false # # Instances may overwrite the class value in the same way: # |