method
merge
v4.2.1 -
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Class: ActiveRecord::SpawnMethods
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- What's this?
merge(other)
public
Merges in the conditions from other, if other is an ActiveRecord::Relation. Returns an array representing the intersection of the resulting records with other, if other is an array.
Post.where(published: true).joins(:comments).merge( Comment.where(spam: false) ) # Performs a single join query with both where conditions. recent_posts = Post.order('created_at DESC').first(5) Post.where(published: true).merge(recent_posts) # Returns the intersection of all published posts with the 5 most recently created posts. # (This is just an example. You'd probably want to do this with a single query!)
Procs will be evaluated by merge:
Post.where(published: true).merge(-> { joins(:comments) }) # => Post.where(published: true).joins(:comments)
This is mainly intended for sharing common conditions between multiple associations.
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noniq -
March 27, 2012
4 thanks
Makes it possible to use a scope through an association
This is a very useful method if you want to to use a scope through an association:
class Book < ActiveRecord::Base scope :available, where(:available => true) end class Author < ActiveRecord::Base has_many :books scope :with_available_books, joins(:books).merge(Book.available) end # Return all authors with at least one available book: Author.with_available_books
See http://asciicasts.com/episodes/215-advanced-queries-in-rails-3 for more info.