34 replies

How to have a "virtual field" in a resource based from another resource?

I have a

Organization

Organization

resource that has a many to many relationship with my

User

User

resource.

That relationship is defined by this field in the

Organization

Organization

resource:

    many_to_many :users, User do
      through UserOrganization

      source_attribute_on_join_resource :organization_id
      destination_attribute_on_join_resource :user_id
    end

    many_to_many :users, User do
      through UserOrganization

      source_attribute_on_join_resource :organization_id
      destination_attribute_on_join_resource :user_id
    end

The

UserOrganization

UserOrganization

resource has a special attribute inside of which defined if the user is an admin inside that organization:

defmodule UserOrganization do
  use Ash.Resource, data_layer: AshPostgres.DataLayer

  attributes do
    attribute :admin?, :boolean, allow_nil?: false, default: false
  end

  relationships do
    ...
  end

  postgres do
    table "users_organizations"
    ...
  end

  ...
end

defmodule UserOrganization do
  use Ash.Resource, data_layer: AshPostgres.DataLayer

  attributes do
    attribute :admin?, :boolean, allow_nil?: false, default: false
  end

  relationships do
    ...
  end

  postgres do
    table "users_organizations"
    ...
  end

  ...
end

What I want to do is to create a

virtual attribute

virtual attribute

in the

Organization

Organization

resource that will tell if that user (the actor) is an admin.

My first approach was to add this new relationship to the resource:

    has_many :users_organizations, UserOrganization

    has_many :users_organizations, UserOrganization

So I can get access to the

UserOrganization

UserOrganization

resource directly from

Organization

Organization

.

After that, I tried creating a calculation that would join that relationship and "extract" the

admin?

admin?

field:

  calculations do
    calculate :admin?, :boolean, expr(users_organizations.admin?)
  end

  calculations do
    calculate :admin?, :boolean, expr(users_organizations.admin?)
  end

That don't work, and I'm not sure how exactly I would filter that calculation to only get the

user_organization

user_organization

from the actor.

My second approach was to try an aggregate:

  aggregates do
    first :admin?, :users_organizations, :admin? do

      filter expr(user_id == ^actor(:id))
    end
  end

  aggregates do
    first :admin?, :users_organizations, :admin? do

      filter expr(user_id == ^actor(:id))
    end
  end

This also doesn't work, and aggregates also will generate a more complex query instead of simply doing the join by

organization_id

organization_id