AF
Ash Framework•3mo ago
tohsig

Convenience functions for many_to_many relationships?

I'm trying to wrap my head around creating convenience functions for many_to_many relationships. Given the resources below, what I'd like to do is have an add_to_hub action in the User module that takes in a Hub record and creates a corresponding UsersToHubs record. How would I go about setting up that action, and is placing a function like this inside of my User resource module at all idiomatic for Ash? I cut off the TestApp.Hubs.Hub module due to character limit, but I set it up the same way as my User module 
defmodule TestApp.Accounts.User do
  use Ash.Resource, domain: TestApp.Accounts

  actions do
    defaults [:read]

    create :create do
      accept [:email, :first_name, :last_name]
    end

    create :add_to_hub do
      #
      # ?
      # 
    end
  end

  attributes do
    uuid_v7_primary_key :id

    attribute :email, :string do
      allow_nil? false
      public? true
    end
  end

  relationships do
    many_to_many :hubs, TestApp.Hubs.Hub do
      through TestApp.Hubs.UsersToHubs
      source_attribute_on_join_resource :user_id
      destination_attribute_on_join_resource :hub_id
    end
  end
end


defmodule TestApp.Hubs.UsersToHubs do
  use Ash.Resource, domain: TestApp.Hubs

  actions do
    defaults [:read, :destroy, create: :*, update: :*]
  end

  attributes do
    create_timestamp :inserted_at
    update_timestamp :updated_at
  end

  relationships do
    belongs_to :hub,
               TestApp.Hubs.Hub,
               primary_key?: true,
               allow_nil?: false

    belongs_to :user,
               TestApp.Accounts.User,
               primary_key?: true,
               allow_nil?: false
  end
end
defmodule TestApp.Accounts.User do
  use Ash.Resource, domain: TestApp.Accounts

  actions do
    defaults [:read]

    create :create do
      accept [:email, :first_name, :last_name]
    end

    create :add_to_hub do
      #
      # ?
      # 
    end
  end

  attributes do
    uuid_v7_primary_key :id

    attribute :email, :string do
      allow_nil? false
      public? true
    end
  end

  relationships do
    many_to_many :hubs, TestApp.Hubs.Hub do
      through TestApp.Hubs.UsersToHubs
      source_attribute_on_join_resource :user_id
      destination_attribute_on_join_resource :hub_id
    end
  end
end


defmodule TestApp.Hubs.UsersToHubs do
  use Ash.Resource, domain: TestApp.Hubs

  actions do
    defaults [:read, :destroy, create: :*, update: :*]
  end

  attributes do
    create_timestamp :inserted_at
    update_timestamp :updated_at
  end

  relationships do
    belongs_to :hub,
               TestApp.Hubs.Hub,
               primary_key?: true,
               allow_nil?: false

    belongs_to :user,
               TestApp.Accounts.User,
               primary_key?: true,
               allow_nil?: false
  end
end
Solution:
I appreciate the very kind "read the manual" haha. Definitely overlooked the many_to_many example when I was reading the docs earlier. So it's basically just: ```elixir update :assign_to_hub do...
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2 Replies
ZachDaniel
ZachDaniel•3mo ago
YOu should look into managing relationships and report back
Solution
tohsig
tohsig•3mo ago
I appreciate the very kind "read the manual" haha. Definitely overlooked the many_to_many example when I was reading the docs earlier. So it's basically just: 
update :assign_to_hub do
  argument :hub_id, :uuid, allow_nil?: false
  change manage_relationship(:hub_id, :hubs, type: :append)
end
update :assign_to_hub do
  argument :hub_id, :uuid, allow_nil?: false
  change manage_relationship(:hub_id, :hubs, type: :append)
end
Very cool.

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