Repositories » Writing Aggregates
Repositories provide a command builder interface which you can use to construct complex commands that can persist nested data, which reflect aggregate structures.
Warning
This API is limited to Create commands only. Use changesets if you need more flexibility and control.
has_many example
Let's say we have :users with :tasks and we'd like to persist a nested data
structure which represents this association.
require 'rom-repository'
rom = ROM.container(:sql, 'sqlite::memory') do |config|
config.default.create_table(:users) do
primary_key :id
column :name, String, null: false
column :email, String, null: false
end
config.default.create_table(:tasks) do
primary_key :id
foreign_key :user_id, :users
column :title, String, null: false
end
config.relation(:users) do
schema(infer: true) do
associations do
has_many :tasks
end
end
end
config.relation(:tasks) do
schema(infer: true) do
associations do
belongs_to :user
end
end
end
end
Once we establish canonical associations for our relations, repositories will know how to prepare commands for persisting nested data.
Let's define a repository which exposes an interface for persisting a new user along with associated tasks:
class UserRepo < ROM::Repository[:users]
def create_with_tasks(user)
users.combine(:tasks).command(:create).call(user)
end
end
user_repo = UserRepo.new(rom)
user_repo.create_with_tasks(
name: 'Jane',
email: 'jane@doe.org',
tasks: [{ title: 'Task 1' }, { title: 'Task 2' }]
)
# => #<ROM::Struct[User] id=1 name="Jane" email="jane@doe.org" tasks=[#<ROM::Struct[Task] id=1 user_id=1 title="Task 1">, #<ROM::Struct[Task] id=2 user_id=1 title="Task 2">]>