How to sort by relationship field

[Rodrigora]

Hi all!

I searched through documentation and code and didn't find a way to sort the records by a relation field.

This is related to #265.

There is someone working on it? If not, I'd be happy to provide PR.

[c-lliope]

Hey, @Rodrigora! Thanks for the suggestion!

Right now this isn't supported. I'm a bit curious about how you'd sort by a relationship - it seems like it would vary depending on whether the relation is a has_many, belongs_to, has_one, or polymorphic relationship.

Can you elaborate on what behavior you'd like to see?

[Rodrigora]

My models are:

class Product
  belongs_to :category
end

class Category
  has_many :product
end

I'd like to sort products by category name, since my products page has the columns id and category (Category column displays the category name).

[sebbean]

I've used this before with spree: https://github.com/activerecord-hackery/ransack

Could be an easy win.

[tomgatzgates]

I've just implemented a very hacky version. This class sits at the bottom of the user controller. I'm not suggesting it as a fix but might help in your case :)

class SearchUser
  def initialize(resolver, term)
    @resolver = resolver
    @term = term
  end

  SEARCH_TABLES = %w(addresses vouchers)
  # Manually add the joins for these tables

  def run
    if @term.blank?
      resource_class.all
    else
      resource_class.uniq
        .joins(:addresses, user_vouchers: [:voucher])
        .where(query, *search_terms)
    end
  end

  private

  delegate to: :resolver

  def query
    prefixed_attributes.map { |attr| "lower(#{attr}) LIKE ?" }.join(' OR ')
  end

  def search_terms
    ["%#{term.downcase}%"] * prefixed_attributes.count
  end

  def prefixed_attributes
    [resource_class] + SEARCH_TABLES.flat_map do |table|
      attributes_for(table).map { |attr| "#{table}.#{attr}" }
    end
  end

  def attributes_for(dashboard)
    Object.const_get(dashboard.classify + 'Dashboard')::ATTRIBUTE_TYPES.select do |_, type|
      type.searchable?
    end.keys
  end

  attr_reader :resolver, :term
end

[hughfm]

Does anyone have any updates on this type of thing? Being able to sort/search by an attribute on a belongs_to association would be a huge win for me.

[carlosramireziii]

@nickcharlton We should look into this one for an upcoming release. There's a proposed solution in #750

[pablobm]

I've been experimenting with this during this last couple of days. Here's what I have so far: https://github.com/thoughtbot/administrate/pull/1506

[connor]

Just wanted to echo my support for a feature like this. Thank you!

[shouichi]

We implemented sorting by relationship field by something like this.

class Comment
	has_one :moderation

	delegate :state, to: :moderation, prefix: true
end

class Moderation
	belongs_to :comment

	enum :approved, :disapproved
end

# comments_controller.rb
def scoped_resource
	if order.order_by?(:moderation_state)
		Comment.joins(:operation).merge(Moderation.order(state: order.direction))
	else
		Comment.default_scoped
	end
end

[pablobm]

I agree with @shouichi that overriding the controller is the best way forward at the moment. I think I would override order instead. See this example, adapted from the example app:

module Admin
  class ProductsController < Admin::ApplicationController
    class OrderByProductMetaTag < Administrate::Order
      def initialize(direction = nil)
        super("product_meta_tag", direction)
      end

      def apply(relation)
        relation.joins(:product_meta_tag).order("product_meta_tags.meta_title" => (direction || "asc").to_sym)
      end

      def ordered_by?(attr)
        attr.to_s == "product_meta_tag"
      end
    end

    def order
      if sorting_attribute == "product_meta_tag"
        OrderByProductMetaTag.new(sorting_direction)
      else
        super
      end
    end
  end
end

The short-term task then is to document this.