Repositories on Rails

How to implement the Repository Pattern in your Rails application, leading to faster tests and more maintainable code.

Transcript

1. Repositories in Rails How and Why to Hide Our Data Layer From Our Business Logic
2. The Repository Pattern is a great way to: • abstract your data layer from your business logic • while speeding up tests • and making code more maintainable
4. • Christopher Coleman • Ramsey Solutions, SmartDollar • B2B, SaaS, Educational, Financial Wellness
5. User Enrollment Company
12. User Enrollment Company API APP Eligibility
24. • Easy to use • Hard to maintain
28. Real-world Functional Ruby Southeast Ruby 2017
29. • Functional “process” objects • Injected dependencies • Immutable state
30. class ChangesUserRole attr_reader :users_repository def initialize(users_repository: default_users_repository) @users_repository = users_repository end def call(user:, new_role:) users_repository .for(user) .grant_role(new_role) .tap do |updated_user| yield updated_user if block_given? end end def default_users_repository Api::Users end end
31. • LaunchPlan::Create • Create launch plan • Create tasks • Schedule tasks on timeline • LaunchPlan::Update • Update launch plan • Create/update/delete tasks • Reschedule tasks on timeline
35. VS
36. • Active Record Pattern: • Smart Mutable Record Objects • Dynamic, lazily evaluated associations • Repository Pattern: • Dumb Immutable Record Structs • Static, preloaded associations
37. Active Record Data Model Query Interface Repository Pattern Data Model Query Interface VS
38. VS
39. VS
41. • ROM-RB • http://rom-rb.org/ • Hanami::Model • https://github.com/hanami/model • http://hanamirb.org/
44. & What would Do?
45. module Api module Users class << self delegate :authenticate, :create, to: :user_class def user_class ActualApi::User end end end end
46. module Api class Users class << self delegate :find, :update, to: :user_class alias_method :for, :new end delegate :find, :update, to: :class attr_reader :instance def initialize(instance) @instance = instance end def grant_role(role) if update(instance.id, role: role) return find(instance.id) end raise InvalidRoleGrant end end end
47. module Api class Users; end class Enrollments; end class Companies; end class Tasks; end # ... end
50. • Delete existing implementation • Rewrite it • Update repositories to call new interface.
52. • Create public API for repository • implemented via ActiveRecord or Hanami::Model • Replace all ActiveRecord model references with Repository calls • Sigh contentedly when my test suite execution time drops • Rinse and repeat
53. class UserLesson < ApplicationRecord def self.for_users(users) where(user_id: users.map(&:id)) end def user Api::Users.find(user_id) end end class Api::Users def self.with_lessons(users) user_lessons = UserLesson.for_users(users).group_by(&:user_id) users.map do |user| user.with(lesson: user_lessons[user.id].lesson) end end end
55. The Repository Pattern is a great way to: • abstract your data layer from your business logic • while speeding up tests • and making code more maintainable
58. • Christopher Coleman • @mellowfish • Slides will be posted on my twitter soon. Have a nice lunch!