Hopscotch

Simplifying complex business logic

Transcript

1. HOPSCOTCH SIMPLIFYING COMPLEX BUSINESS LOGIC
2. AGENDA: - wtf hopscotch - various usage examples - how we actually use it in prod
3. A TAIL OF THE RAILS
4. In a world where things are simple, Rails *generates* success.
5. MONTH 1: !
6. KILLER SICK OBJECT class User < ActiveRecord::Base def full_name "#{first_name} #{last_name}" end alias_method :to_s, :full_name def fourty_two 42 end end
7. SUCCESS !"
8. MONTH 2: ☔
9. class User < ActiveRecord::Base # ... before_validation(on: :create) do create_password end def create_password return if plain_password.present? # I'm creating.. why would this already exist? w1 = Word.randomised.simple_word.first.word # adding dependent object to creation. self.plain_password = "#{ w1 }#{ "%02d" % rand(100) }" # !" set_password # I call another method..? end def set_password return if !changed.include?("plain_password") # active record dirty? maybe? self.password = plain_password self.password_confirmation = plain_password end # ... end
10. !
11. IT STARTS SMALL before_validation(on: :create) do create_password end - Adds complexity to the `Student` model. - Makes the process of creating a `Student` depend on other objects (hard to know from the outside) - Can make things very hard to test. - Makes this type of functionality hard to reuse.
12. SUCCESS!!1 !"!" IT'S STILL WORKING!
13. MONTH 6: !
14. IT GROWS before_validation(on: :create) do create_password set_login_from_name create_info end before_validation do set_info_student set_password end after_create do initialize_student set_access_all_areas if demo_only? end before_save do set_school_from_teacher set_inactive_if_no_teacher set_active_if_teacher end after_save do add_trial_if_home_school_linked update_country_code! flag_for_update_parent clear_cart_items if parent_id_changed? end after_destroy do flag_for_update_parent clear_cart_items end after_commit do update_parent end
15. !
16. ! !!!!!!! !!!!!!! !!!!!! (IT IS NOT FUN)
17. WHY SO BAD? > Hard to test > Hard to reason about (wtf object?) > Debugging == !" > Explicit > Magic (almost always!)
22. IS THERE AN EASIER WAY?
23. INTRODUCING...
24. ✨ HOPSCOTCH ✨ RAZZLE DAZZLE
25. WHAT IS IT EVEN? - A way to simplify interactions within a system - A way to reuse similar steps in a complex system - Very declarative way to express business rules - Safe! Helps ensure everything is atomic*
26. WHAT IS IT MADE OF? - Hopscotch::Step - Hopscotch::StepComposer - Hopscotch::Runner
27. HOPSCOTCH::STEP - TL;DR: function returns either `success!` or `failure!` - function protocol (must conform to the pattern) - a type specification Step1: !
28. SIMPLE EXAMPLE -> { Hopscotch::Step.success! } abc = -> (number) do if number >= 1 Hopscotch::Step.success! else Hopscotch::Step.failure! end end # abc.call(100) => Hopscotch::Step.success! # abc.(0) => Hopscotch::Step.failure!
29. SIMPLE EXAMPLE def update_record(record:, attributes:) if record.validate(attributes) && record.save Hopscotch::Step.success! # must return this else Hopscotch::Step.failure!(record) # or return this end end
30. SIMPLE EXAMPLE def redeem_discount_code(code:, parent:) if CodeRedeemer.new(parent).redeem(code) Hopscotch::Step.success! else Hopscotch::Step.failure!("Not a valid code.") end end
31. SIMPLE EXAMPLE def move_teacher(teachers, new_school) teacher_ids = teachers.pluck(:id) if ::Teacher.where(id: teacher_ids).update_all(school_id: new_school.id) Hopscotch::Step.success! else Hopscotch::Step.failure! end end
32. BIT MORE INVOLVED def award_trading_card(student, realm) return Hopscotch::Step.failure!('Not eligible for trading card') unless student.eligible_for_trading_card return Hopscotch::Step.failure!('No trading cards for realm') unless trading_card = random_trading_card(realm) if student_trading_card = create_student_card(student, trading_card) Hopscotch::Step.success!(student_trading_card) else Hopscotch::Step.failure!('Error creating student trading card') end end private def random_trading_card(realm) TradingCard.random_from_realm(realm) end def create_student_card(student, trading_card) student_trading_card = StudentTradingCard.create(student: student, trading_card: trading_card) student.eligible_for_trading_card = false student.save student_trading_card end
33. !
34. HOPSCOTCH::STEPCOMPOSER - TL;DR: combines steps - Composes a list of functions into a single function - Checks errors via "typechecking" the Step's return value Step1: ! Step2: " StepComposer: #
35. HUH? success_step = -> { Hopscotch::Step.success! } fail_step = -> { Hopscotch::Step.failure!("bad") } success_reduced_fn = Hopscotch::StepComposer.compose_with_error_handling( success_step, success_step, success_step ) error_reduced_fn = Hopscotch::StepComposer.compose_with_error_handling( success_step, fail_step, # will catch the failure here success_step )
36. SIMPLE EXAMPLE def setup_teacher_trial(teacher) Hopscotch::StepComposer.call_each( -> { update_email_flags(teacher) }, -> { create_teacher_subscription(teacher) }, -> { create_demo_student(teacher) }, -> { create_school_class(teacher) } ) end
37. THERE IS NO MAGIC Hopscotch::StepComposer.call_each(steps) # is just calling Hopscotch::StepComposer.compose_with_error_handling(steps).call
38. !
39. HOPSCOTCH::RUNNER - Wraps a function in a transaction block - Calls a success or failure callback depending on the function result - Is the pipeline that ties everything together Runner: !, success: ", failure: #
40. SIMPLE CONTROLLER EXAMPLE class TeachersController < ApplicationController def setup_trial Hopscotch::Runner.call( setup_teacher_trial, success: -> { redirect_to dashboard_path, notice: "Howdy." }, failure: -> (teacher) { render :new } ) end private def setup_teacher_trial(teacher) Hopscotch::StepComposer.call_each( -> { update_email_flags(teacher) }, -> { create_teacher_subscription(teacher) }, -> { create_demo_student(teacher) }, -> { create_school_class(teacher) } ) end end
41. CSV EXAMPLE def import(file, success:, failure:) ::Hopscotch::Runner.call_each( # convenience method -> { validate_student_file(file) }, -> { upload_student_file(file) }, success: success, failure: failure ) end
42. THERE IS NO MAGIC Hopscotch::Runner.call_each(steps, success: success, failure: failure) # is just calling Hopscotch::Runner.call( Hopscotch::StepComposer.compose_with_error_handling(steps), success: success, failure: failure )
43. THAT'S ALL THERE IS TO IT
44. ...
45. LETS SEE IT IN PRACTICE
46. HOW WE USE IT AT BLAKE
47. TWO DURS ! Services ! Workflows
48. SERVICES module Service::AwardEggs extend self EGGS = 10 def call(student, eggs = EGGS) if EggLedger.new(student).add(eggs) Hopscotch::Step.success!("Eggs were awarded successfully.") else Hopscotch::Step.failure!("Could not award eggs.") end end end
49. SERVICES module Service::AwardStudent extend self def call(student) Hopscotch::StepComposer.call_each( -> { Service::AwardEggs.call(student) }, -> { Service::AwardTradingCard.call(student) }, -> { Service::AwardTrophy.call(student) } ) end end
50. WHAT IS A SERVICE - Wrapper for a Hopscotch::Step - (or Hopscotch::StepComposer) - Conform to 1 public `#call` method - Does 1 small thing - Great for reuse
51. WORKFLOWS module Workflow::School::MigrateToRex extend self def call(school, success:, failure:) ::Hopscotch::Runner.call( rex_migration_steps(school), success: -> { success.call("Migrated school: #{school.name} to the new version of REX") }, failure: -> { failure.call("Migration failed! Please contact support") } ) end def rex_migration_steps(school) ::Hopscotch::StepComposer.call_each( -> { ::Service::School::StartRexMigration.call(school) }, -> { ::Service::School::MarkEnabledForRex.call(school) }, ) end end # Call'em success = -> (message) { puts message } failure = -> (error) { puts error } Workflow::School::MigrateToRex.call(school, success: success, failure: failure)
52. CALLBACK WORKFLOW EXAMPLE
53. WHAT IS A WORKFLOW - Wrapper for a Hopscotch::Runner - Used to handle control flow for the entire process - Makes callbacks fun again! Passed in. Declarative. Awesome.
54. RECAP - Hopscotch::Step - simple function that returns success! or failure! - Hopscotch::StepComposer - composes steps together to create 1 function - Hopscotch::Runner - calls 1 function and calls failure/success depending on functions results
55. THANKS - Blake Education: http://dev.blake.com.au/ - Hopscotch: https://github.com/blake-education/hopscotch - Twitter: @gogogarrett