1 year with rom on production
TRANSCRIPT
@gotar | @oskarszrajer gotar.info
Oskar Szrajer
One year with
on production
What is ROM (Ruby Object Mapper)
https://github.com/orgs/rom-rb
PERSISTENCE & MAPPING TOOLKIT FOR RUBY
http://rom-rb.org
Author of ROM
Piotr Solnica | @_solnic_ | http://solnic.eu
author of ROM, Virtus, Dry-*, Rodakase, ...
Community
• dozen of devs
• very active Gitter channelhttps://gitter.im/rom-rb/chat
• stable API >1.0v
• battle tested on production
History of ROM
• successor of DataMapper - aka DataMapper v2
• first commit - Feb 1 2012
• first version - v0.1 - Jun 15 2013
• first public version - v0.6 - Mar 22, 2015
• v1.0 - stable API - Jan 6, 2016
Core ideas
• reduced global state to minimum
• immutability
• mix OO with FP
• blazing fast
Core concepts
• Configuration
• Relations
• Commands
• Mappers
Configurationrequire 'rom'
config = ROM::Configuration.new( :sql, 'postgres://localhost/rom_repo'
)
rom = ROM.container(config)
rom.gateways[:default] # #<ROM::SQL::Gateway:0x007fde7a087158>
ROM::Configuration.new(
default: [:sql, 'postgres://localhost/db'],
legacy: [:sql, 'mysql://localhost/legacy_db'],
marketing: [:yesql, 'postgres://localhost/db', path: './sql'],
cache: [:redis, 'redis://localhost'],
csv: [:csv, File.expand_path('./data.csv', __FILE__],
events: [:event_store, '127.0.0.1:1113']
# ...
)
Relations
class Users < ROM::Relation[:sql] def by_id(id) where(id: id) end end
rom.relation(:users).by_id(1).to_a # [{:id=>1, :name=>"Jane"}]
Everything is lazy (callable)
rom.relation(:users).by_id(1) #<Db::Relations::Users dataset=#<Sequel::Postgres::Dataset: "SELECT "id", ...
rom.relation(:users).by_id(1).call # [{:id=>1, :name=>"Jane"}]
rom.relation(:users).by_id(1).only(:id).to_a # [{:id=>1}]
rom.relation(:users).by_id(1).only(:id).one # {:id=>1}
Commandsclass Create < ROM::Commands::Create[:sql] relation :users register_as :create
result :one end
create_user = rom.command(:users).create
create_user.call(name: 'Jack') # {id: 2, name: 'Jack'}
class Create < ROM::Commands::Create[:sql] relation :users register_as :create
input NewUserParams validator UserValidator
result :one end
class AuthorWithBooks < ROM::Commands::Create[:sql] #...
end
create_authors_with_books = rom.command(:authors) do |authors| authors.create(:books)
end
create_authors_with_books[authors: evaluated_authors]
# {:id=>1, :code=>"jd001", :name=>"Jane Doe", :email=>"[email protected]"} # {:id=>1, :author_id=>1, :title=>"First", :published_on=>#<Date: 2010-10-10 ((2455480j,0s,0n),+0s,2299161j)>} # {:id=>2, :author_id=>1, :title=>"Second", :published_on=>#<Date: 2011-11-11 ((2455877j,0s,0n),+0s,2299161j)>} # {:id=>3, :author_id=>1, :title=>"Third", :published_on=>#<Date: 2012-12-12 ((2456274j,0s,0n),+0s,2299161j)>}
Mappersclass UsersMapper < ROM::Mapper
relation :users
register_as :entity
attribute :id
attribute :name
attribute :age do
rand(18..90)
end
end
users = rom.relation(:users).as(:entity)
users.call
[
{ id: 1, name: "Jane", age: 22 },
{ id: 2, name: "Jack", age: 64 }
]
Pipelines (everything that responds to #call
can be a mapper)
only_name = -> input { input.map{|u| u[:name]} }
upcase = -> input { input.map{|x| x.upcase} }
users = rom.relation(:users)
result = users >> only_name >> upcase
result.to_a
> ["JANE", "JACK"]
Domain data types & Repositories
class User < Dry::Types::Value attribute :name, Types::Strict::String
end
class UserRepo < ROM::Repository relation :users
def all users.select(:name).as(User).to_a
end end
user_repo = UserRepo.new(rom)
user_repo.all
> [#<User name="Jane">, #<User name="Jack">]
My story
My story
Both project use similar technologies:
• Roda (as HTTP layer)
• ROM
• Yaks (JSON API)
Request cycle
ParamsObject >> Validator >> ROM >>
Mapper(s) >> JSON API Mapper
Mapping & coercion layer
Mapping & coercion layer
combine (or change)
data
convert data to json api format
CQRS
combining dataclass UserRepository < ROM::Repository::Base relations :users, :tasks
def with_tasks(id) users.by_id(id).combine_children(many: tasks) end end
user_repo.with_tasks.to_a
# [#<ROM::Struct[User] id=1 name="Jane" tasks=[#<ROM::Struct[Task] id=2 user_id=1 title="Jane Task">]>, #<ROM::Struct[User] id=2 name="Jack" tasks=[#<ROM::Struct[Task] id=1 user_id=2 title="Jack Task">]>]
pros
• separating persistence from application &
encouraging that boundary
• ability to choose appropriate storage (SQL, NoSQL, ...),
but keeping the same API
• possibility to pull from different data sources,
and combine everything together
pros
• easy way to map (manipulate, coerce) data
• freedom
• community
cons• commands (right now repository do not support them,
force to use very low level API, should be done before v2)
• hard to learn (many new concepts)
• lack of documentation (community will help you)
(currently community works to fix it, and there is always
someone sitting on Gitter to help you)
Worth it?
Q&A@gotar | @oskarszrajer gotar.info
Thx@gotar | @oskarszrajer gotar.info