diff options
Diffstat (limited to 'activerecord/lib')
| -rw-r--r-- | activerecord/lib/active_record/identity_map.rb | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/identity_map.rb b/activerecord/lib/active_record/identity_map.rb index cad3865f03..61221f24b4 100644 --- a/activerecord/lib/active_record/identity_map.rb +++ b/activerecord/lib/active_record/identity_map.rb @@ -12,7 +12,34 @@ module ActiveRecord # In order to enable IdentityMap, set <tt>config.active_record.identity_map = true</tt> # in your <tt>config/application.rb</tt> file. # - # IdentityMap is disabled by default. + # IdentityMap is disabled by default and still in development (i.e. use it with care). + # + # == Associations + # + # Active Record Identity Map does not track associations yet. For example: + # + # comment = @post.comments.first + # comment.post = nil + # @post.comments.include?(comment) #=> true + # + # Ideally, the example above would return false, removing the comment object from the + # post association when the association is nullified. This may cause side effects, as + # in the situation below, if Identity Map is enabled: + # + # Post.has_many :comments, :dependent => :destroy + # + # comment = @post.comments.first + # comment.post = nil + # comment.save + # Post.destroy(@post.id) + # + # Without using Identity Map, the code above will destroy the @post object leaving + # the comment object intact. However, once we enable Identity Map, the post loaded + # by Post.destroy is exactly the same object as the object @post. As the object @post + # still has the comment object in @post.comments, once Identity Map is enabled, the + # comment object will be acciddently removed. + # + # This incosistency is meant to be fixed in future Rails releases. # module IdentityMap |