Associations

Changesets can be associated with each other using Changeset#associate method, which will automatically set foreign keys for you, based on schema associations. Let's define :users relation that has many :tasks:

class Users < ROM::Relation[:sql]
  schema(infer: true) do
    associations do
      has_many :tasks
    end
  end
end

class Tasks < ROM::Relation[:sql]
  schema(infer: true) do
    associations do
      belongs_to :user
    end
  end
end

With associations established in the schema, we can easily associate data using changesets and commit them in a transaction:

task = tasks.transaction do
  user = users.changeset(:create, name: 'Jane').commit

  new_task = tasks.changeset(:create, title: 'Task One').associate(user)

  new_task.commit
end

task
# {:id=>1, :user_id=>1, :title=>"Task One"}