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[KRUG] Architecture. The reclaimed years.

[KRUG] Architecture. The reclaimed years.

A short intro into clean architecture for Ruby apps based on dry-system gem.

Piotr Solnica

March 20, 2018
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  1. "The top level architecture of my rails application, did not

    scream its intent at you, it screamed the framework at you, it screamed Rails at you" — Uncle Bob 5
  2. 12

  3. 13

  4. 17

  5. 18

  6. class CreateUser attr_reader :user_repo, :validator, :mailer def initialize(user_repo:, validator:, mailer:)

    @user_repo = user_repo @validator = validator @mailer = mailer end end 20
  7. 24

  8. > Minimize state in classes > Don't rely on class

    state at runtime > Don't rely on monkey-patching 25
  9. > Using singleton methods couple your code to class/ module

    constants > Singleton methods easily lead to awkward, procedural code 31
  10. > Minimize usage of singleton methods, they are only good

    as "builder" methods, or top-level configuration APIs > Don't use them at runtime, objects are 10 x better and more flexible 32
  11. > An architecture for Ruby applications > Based heavily on

    lightweight dependency injection > Allows you to compose an application from isolated components 34
  12. 35

  13. # app/system/app.rb require 'dry/system/container' class App < Dry::System::Container configure do

    |config| config.auto_register = %w(lib) end load_paths! 'lib', 'system' end 40
  14. SIMPLE OBJECT COMPOSITION require 'import' module Users class CreateUser include

    Import['repos.user_repo'] def call(params) user_repo.create(params) end end end 41
  15. YOUR APP IS THE ENTRY POINT TO YOUR SYSTEM ∞

    pry -r ./system/app [1] pry(main)> App['users.create_user'] => #<Users::CreateUser:0x00007ff3a1b2e520..> [2] pry(main)> App['repos.user_repo'] => #<Repos::UserRepo:0x00007ff3a11b0890..> 42
  16. 43

  17. TESTING IN ISOLATION require 'users/create_user' RSpec.describe Users::CreateUser do subject(:create_user) do

    Users::CreateUser.new end describe '#call' do it 'returns created user' do user = create_user.call(id: 1, name: 'Jane') expect(user).to eql(id: 1, name: 'Jane') end end end 44
  18. # system/web.rb require_relative 'app' require 'roda' class Web < Roda

    opts[:api] = App plugin :json route do |r| r.post 'users' do api['users.create_user'].call(r[:user]) end end def api self.class.opts[:api] end end 48
  19. #!/usr/bin/env ruby require "bundler/setup" require "hanami/cli" require "json" require_relative '../system/boot'

    module Commands extend Hanami::CLI::Registry class CreateUser < Command desc "Creates a user" argument :user, desc: "User data" def call(user: nil, **) params = JSON.parse(user) output = App['users.create_user'].call(params) puts "Created #{output.inspect}" end end register "create_user", CreateUser end Hanami::CLI.new(Commands).call 51
  20. WEB INPUT AS PRE-PROCESSED RACK PARAMS r[:user] # { "id"

    => 1, "name" => "Jane" } CLI INPUT AS A PLAIN JSON STRING '{"id":1,"name":"Jane"}' 54
  21. 58

  22. CLEAN ARCHITECTURE > Ruby app comes first > Respecting boundaries

    > Object composition > User interface as an extension of your Ruby app 59
  23. MORE THINGS TO CHECK OUT > Boundaries talk by Gary

    Bernhardt > dry-system on GitHub > sample app from slides on GitHub 61