Accept belongs_to assoc. keys in ActiveRecord queries

Allows you to specify the model association key in a belongs_to
relationship instead of the foreign key.

The following queries are now equivalent:

Post.where(:author_id => Author.first)
Post.where(:author => Author.first)

PriceEstimate.where(:estimate_of_type => 'Treasure', :estimate_of_id => treasure)
PriceEstimate.where(:estimate_of => treasure)

1 files changed, 7 insertions, 0 deletions

diff --git a/guides/source/active_record_querying.textile b/guides/source/active_record_querying.textile
index 96ae5b2972..e21b86721f 100644
--- a/guides/source/active_record_querying.textile
+++ b/guides/source/active_record_querying.textile
@@ -465,6 +465,13 @@ The field name can also be a string:
 Client.where('locked' => true)
 </ruby>
 
+In the case of a belongs_to relationship, an association key can be used to specify the model if an ActiveRecord object is used as the value. This method works with polymorphic relationships as well.
+
+<ruby>
+Post.where(:author => author)
+Author.joins(:posts).where(:posts => {:author => author})
+</ruby>
+
 NOTE: The values cannot be symbols. For example, you cannot do +Client.where(:status => :active)+.
 
 h5(#hash-range_conditions). Range Conditions