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ruby-on-railsactiverecordrelation

How to return an empty ActiveRecord relation?

If I have a scope with a lambda and it takes an argument, depending on the value of the argument, I might know that there will not be any matches, but I still want to return a relation, not an empty array:

scope :for_users, lambda { |users| users.any? ? where("user_id IN (?)", users.map(&:id).join(',')) : [] }

What I really want is a "none" method, the opposite of "all", that returns a relation that can still be chained, but results in the query being short-circuited.

Solution

  • There is a now a "correct" mechanism in Rails 4:

    >> Model.none 
=> #<ActiveRecord::Relation []>