Up-Down Development and "DSL-first" approach

Transcript

1. Up-Down Development and
 “DSL-first” approach Melnyk Volodymyr
 Lviv, 2015
2. Who am I? • Software craftsman with ~7y experience • Atheist • Libertarian and anarchs- capitalist • Scientist and skeptic • A man with business/ economics mind
3. Chaos-Driven Development
4. before_create :set_user class GodObjectsManager validates :user, on: create, unless: -> (r) { r.is_valid? } def index
 if user
 …
 if category
 elsif order.price > 100500 end else # TODO: fix this end end before_action :do_something, only: [:index, :show] @user = User.joins(:roles).where(params[:user_id]) describe “index” do
 it “should be success” do
 expect(response.status).to be 200
 end end Spaghetti - Oriented Development
5. Domain-Driven Development Better, but isn’t great
6. Up-Down Development Everywhere
8. Presentation Layer Presentation Layer is the same as User Interface and is responsible for presenting data to user and interpreting user’s commands. We can split it conventionally to forms and views.
9. Application Layer It defines tasks that application should do and coordinates them between Domain Entities/ Aggregates and Services.
10. Domain Layer Domain Layer or Model Layer or Domain Model Layer is the main part of your app, which stores all domain-specific logic and describes business-processes that are automatized with the help it.
11. Infrastructure Layer Infrastructure Layer does all the dirty job.
12. UI and Magic How user sees your application
13. – Volodymyr Melnyk “For user UI is the application.”
14. D is for Dependency Inversion Principle Split off your app on layers that should not be dependent on layers below.
15. Layers testing …or how unit tests becomes acceptance, functional and integration tests
16. • Write unit tests for screen or screens of a feature for your presentation layer. • White correct static presentation code which passes the tests. • Add more contexts and edge-cases to your tests. • Update UI for new tests. • Make UI dynamic through adding mocked Domain Model and Application layers (refactor).
17. “Make UI dynamic” means your Unit-tests becomes functional, integration or even acceptance.
18. “DSL-first” approach as evolution of Up-Down Development
19. “The whole is greater than the sum of its parts” - Aristotle
20. SLOC - System as a Logic Over his Components
21. DSL implementation is the system …code written in DSL is the system rules and/or state
22. Example of refactoring using “DSL-first” approach
26. • Great abstraction and single interface for all SOAP/ RESTful APIs. • No vendor lock. • Easy to read and maintain code. • Smaller number of code defects.
27. Example from Better Than Everybody Software
28. Abstract Query Interfact How to get real DB-agnosticism and split off layers?
30. Thank you!
31. Do you have any questions?