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author | Neeraj Singh <neerajdotname@gmail.com> | 2010-07-09 16:39:34 -0400 |
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committer | Neeraj Singh <neerajdotname@gmail.com> | 2010-07-09 16:39:34 -0400 |
commit | 44b752bea148b9df8f4d806e410e30fff26f680e (patch) | |
tree | 04ba9007499c78edb02ac376ccc78b4ac5cf9b44 /railties/guides | |
parent | 2f04c8785540597b02a265324c91267f09ddd07c (diff) | |
download | rails-44b752bea148b9df8f4d806e410e30fff26f680e.tar.gz rails-44b752bea148b9df8f4d806e410e30fff26f680e.tar.bz2 rails-44b752bea148b9df8f4d806e410e30fff26f680e.zip |
expanding on :uniq option in has_many
Diffstat (limited to 'railties/guides')
-rw-r--r-- | railties/guides/source/association_basics.textile | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/railties/guides/source/association_basics.textile b/railties/guides/source/association_basics.textile index c69f2ae8c9..bc08874a30 100644 --- a/railties/guides/source/association_basics.textile +++ b/railties/guides/source/association_basics.textile @@ -1371,7 +1371,47 @@ The +:through+ option specifies a join model through which to perform the query. h6(#has_many-uniq). +:uniq+ -Specify the +:uniq => true+ option to remove duplicates from the collection. This is most useful in conjunction with the +:through+ option. +Specify the +:uniq => true+ option to remove duplicates from the collection. It only works with +:through+ option. + +<ruby> +class Person < ActiveRecord::Base + has_many :readers + has_many :posts, :through => :readers + + def self.lab + person = Person.create(:name => 'john') + p = Post.create(:name => 'a1') + person.posts << p + person.posts << p + person.reload + puts person.posts.inspect #=> [#<Post id: 5, name: "a1">, #<Post id: 5, name: "a1">] + puts Reader.all.inspect #=> [#<Reader id: 12, person_id: 5, post_id: 5>, #<Reader id: 13, person_id: 5, post_id: 5>] + end +end +</ruby> + +In the above case +readers+ table has two records and +person.posts+ brings out both of these records even though these records are basically pointing to the same +post+ record. + +Now let's add +uniq => true+ option. + +<ruby> +class Person + has_many :readers + has_many :posts, :through => :readers, :uniq => true + + def self.experiment + person = Person.create(:name => 'honda') + p = Post.create(:name => 'a1') + person.posts << p + person.posts << p + person.reload + puts person.posts.inspect #=> [#<Post id: 7, name: "a1">] + puts Reader.all.inspect #=> [#<Reader id: 16, person_id: 7, post_id: 7>, #<Reader id: 17, person_id: 7, post_id: 7>] + end +end +</ruby> + +In the above case +readers+ table still has two records. However +person.posts+ will show only one +post+ record because collection will load only +unique+ records. h6(#has_many-validate). +:validate+ |