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Order Rails Query by Virtual Attribute

Rails' scopes don't work well with virtual attributes since they resolve to a SQL query. Instead you can throw them in an array and then sort by a virtual attribute.

Have you tried and failed to order a rails query by a virtual attribute, being told the column isn't in the database (when, in fact, you already knew that)?

Let's say you have a User model that has a name attribute that you've split up on the fly. Something like this.

class User < ActiveRecord::Base

def first_name
return email if name.nil?
name.split(' ').first
end

def last_name
return email if name.nil?
name.split(' ').last
end

end

You've probably tried and failed with a scope like this.

scope :by_name, -> { order('last_name asc') }

What you have to do is first load the objects you want into memory and then use Ruby's sort_by array method to sort the collection of objects. So, something like this would work.

scope :by_name, -> { all.to_a.sort_by(&:last_name) }

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