Wsrtjtyk

How can I combine two scopes to get both results of them in one query, when they are polymorphic associations? I have this models:

class Vendor < ApplicationRecord

  has_many :shipping_method_registers, as: :shipper

  has_many :shipping_methods, through: :shipping_method_registers

end



class City < ApplicationRecord

  has_many :shipping_method_registers, as: :shipper

  has_many :shipping_methods, through: :shipping_method_registers

end



class ShippingMethodRegister < ApplicationRecord

  belongs_to :shipping_method

  belongs_to :shipper, polymorphic: true

end



class ShippingMethod < ApplicationRecord

  has_many :shipping_method_registers, dependent: :destroy, autosave: true

  has_many :city_zones, through: :shipping_method_registers, source: :shipper,

                        source_type: "City"

  has_many :vendors, through: :shipping_method_registers, source: :shipper,

                     source_type: "Vendor"

end

I want to get the shipping methods of a vendor AND a city combined, but only distinct results. I tried it with

> vendor.shipping_methods.or(city.shipping_methods)

ArgumentError: Relation passed to #or must be structurally compatible. Incompatible values: [:joins]

from /usr/local/bundle/gems/activerecord-5.2.0/lib/active_record/relation/query_methods.rb:634:in `or!'

And also with

> vendor.shipping_methods.merge(city.shipping_methods)

But this only returns the shipping methods of the city. I could merge them in Ruby, but I'd like to do it in one query.