Support getting criteria for has_many: through: associations

[robertjpayne]

I can't seem to find a way to get a valid criteria object for an association, I dug through the source and looked at what's given in the reflection API but it doesn't seem there is a way to get a criteria object?

It would be really great for instances to extend it or manipulate the query. In this particular case I am attempting to apply a offset and limit based on API input to a association.

[nviennot]

That should work, can you post some sample code?

[robertjpayne]

Might be because it's a has_many through?

require 'nobrainer'
require 'excon'
require 'logger'

logger = Logger.new(STDOUT)

NoBrainer.configure do |c|
  c.app_name = 'test'
  c.environment = 'development'
  c.rethinkdb_urls = [c.default_rethinkdb_url]
  c.logger = logger
end

class User
  include NoBrainer::Document

  field :name, type: String, required: true

  has_many :followingships, class_name: 'Followship', foreign_key: :follower_id, dependent: :restrict
  has_many :followerships, class_name: 'Followship', foreign_key: :following_id, dependent: :restrict

  has_many :following, through: :followingships
  has_many :followers, through: :followerships

end

class Followship
  include NoBrainer::Document

  field :follower_id, type: String, required: true, index: true
  field :following_id, type: String, required: true, index: true

  belongs_to :follower, class: 'User'
  belongs_to :following, class: 'User'

  index :follower_id_and_following_id, [:follower_id, :following_id]

end

NoBrainer.sync_indexes

User.delete_all
Followship.delete_all

robert = User.create!(name: 'Robert')
karen = User.create!(name: 'Karen')
pablo = User.create!(name: 'Pablo')
ivan = User.create!(name: 'Ivan')
john = User.create!(name: 'John')
andrea = User.create!(name: 'Andrea')

Followship.create!(follower: robert, following: karen)
Followship.create!(follower: robert, following: pablo)
Followship.create!(follower: robert, following: john)
Followship.create!(follower: robert, following: ivan)
Followship.create!(follower: robert, following: andrea)

Followship.create!(follower: john, following: robert)
Followship.create!(follower: john, following: karen)

Followship.create!(follower: andrea, following: robert)

current_user = john
user = robert

puts robert.followers.offset(2).limit(1).to_a

[robertjpayne]

Ah yea looks because it's a has_many though hmm.

[nviennot]

Oh indeed. With has_many_through you don't get a criteria. I'll see how to work around with that.

[nviennot]

This is actually complicated to implement, so I'll punt for now.

You can do something like this:

robert.followerships.join(:follower).offset(x).limit(1).map(&:follower)

You can also use eager_load instead of join. Not sure which is faster.

[robertjpayne]

@nviennot yea that is what I am doing right now, it works would just be nice if it was supported otherwise.

[nviennot]

I agree.

btw, how's your experience with NoBrainer so far?

[robertjpayne]

@nviennot really good. I'm pretty new to building backend API's so I can't really compare too much.

I think the only really hard part I've had to deal with is really custom associations that us a lot of RQL to build the association ( but they are reliant on properties in the model instance so they can't just be a scope )

Thanks again for the hard work! I also saw a few tickets over on RethinkDB's issue tracker (2PC, Celluloid) you've been trying to get sorted which is great.