How to write code that fits the domain model

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https://stanko.io/keep-it-boring-dont-surprise-me-52opnwWR6CBh

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# Code Summary for article# # https://stanko.io/keep-it-boring-dont-surprise-me-52opnwWR6CBh# part 1/4 : Sample code surprising and simplePurchaseChargerService( purchase: PurchaseBuilderService.new(line_items: line_items).call, form: purchase_form, user: current_user).call# Why the code ☝️ is surprising: # > "Nobody expects things like `PurchaseChargerService` and `PurchaseBuilderService` to exist, yet alone that you have to call those in succession with a form object and the current user to make a purchase."user.purchase(line_items) .charge(authorization_code: params[:authorization_code])# Why the code ☝️ is simple?# > "While most people working on a web shop expect that a user can just purchase something, and that a purchase can be charged."# Part 2/4 : Lesson 1: Embrace the domain you are working with# "Naming something after what it does and putting it next to the thing it works with tells a story that can help people understand what’s going on"# Rename (location: app/services/purchase_charger_service.rb)class PurchaseChargerService; end # To (location: app/models/purchases/charger.rb)module Purchases class Charger; end end # Part 3/4 : Lesson 2: Write code that mimics how people think about the domain# "If a `User` can purchase line items, then add a `purchase` method to the User model that accepts line items"class User # @return [Purchase] def purchase(line_items) end end# Part 4/4: Lesson 3: Extract actions into models to tell a story# # "Don’t create new classes just to keep things DRY. If your model has many small or a single large method that deal with a single action, extract it into its own model."class Purchase # @return [Purchases::Charge] def charge(authorization_code:) Purchases::Charger.new.call endend