Repositories » Changeset Transactions & Associations
If you want to commit multiple changesets, it's a good idea to wrap that operation in a
repository transaction. 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:
require 'rom'
rom = ROM.container(:sql, 'sqlite::memory') do |conf|
conf.default.create_table(:users) do
primary_key :id
column :name, String, null: false
end
conf.default.create_table(:tasks) do
primary_key :id
foreign_key :user_id, :users, null: false
column :title, String, null: false
end
conf.relation(:users) do
schema(infer: true) do
associations do
has_many :tasks
end
end
end
conf.relation(:tasks) do
schema(infer: true) do
associations do
belongs_to :user
end
end
end
end
With associations established in the schema, we can easily associate data using changesets and commit them in a transaction:
class UserRepo < ROM::Repository[:users]
commands :create
end
class TaskRepo < ROM::Repository[:tasks]
commands :create
end
task_repo = TaskRepo.new(rom)
user_repo = UserRepo.new(rom)
task = task_repo.transaction do
user = user_repo.create(name: 'Jane')
new_task = task_repo.changeset(title: 'Task One').associate(user)
task_repo.create(new_task)
end
task
# #<ROM::Struct[Task] id=1 user_id=1 title="Task One">
Association name
Notice that
associatemethod can accept a rom struct and it will try to infer association name from it. If this fails because you have an aliased association then pass association name explicitly as the second argument, ie:associate(user, :author)