Rails3: combine scope with OR

问题:

I need to combine name scope with or operator... Something like:

class Product < ActiveRecord::Base
  belongs_to :client

  scope :name_a, where("products.name = 'a'")
  scope :client_b, joins(:client).where("clients.name = 'b'")

  scope :name_a_or_b, name_a.or(client_b)  
end

Thx

回答1:

From Arel documentation

The OR operator is not yet supported. It will work like this: users.where(users[:name].eq('bob').or(users[:age].lt(25)))

This RailsCast shows you how to use the .or operator. However, it works with Arel objects while you have instances of ActiveRecord::Relation. You can convert a relation to Arel using Product.name_a.arel, but now you have to figure out how to merge the conditions.

回答2:

Heres a hack I would use to deal with that missing feature:

class Product < ActiveRecord::Base
  belongs_to :client

  class << self
    def name_a
      where("products.name = 'a'")
    end

    def client_b
      joins(:client).where("clients.name = 'b'")
    end

    def name_a_or_b
      clauses = [name_a, client_b].map do |relation| 
        clause = relation.arel.where_clauses.map { |clause| "(#{clause})" }.join(' AND ')
        "(#{clause})" 
      end.join(' OR ')

      where clauses
    end
  end
end

回答3:

For Rails 3:

Person.where(
  Person.where(name: "John").where(lastname: "Smith").where_values.join(' OR ')
)