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Real-world Functional Ruby Southeast Ruby 2017

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@timriley

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@icelab

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!

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@dry_rb @rom_rb

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PODCASTERS

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“TBA”

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“Programmers at work maintaining a Ruby on Rails application” Eero Järnefelt 
 Oil on canvas, 1893

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user.rb after_save accepts_nested_attributes_for

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⏱ DESIGN STAMINA HYPOTHESIS

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⏱ DESIGN STAMINA HYPOTHESIS

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⏱ DESIGN STAMINA HYPOTHESIS

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⏱ DESIGN STAMINA HYPOTHESIS No design

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⏱ DESIGN STAMINA HYPOTHESIS No design

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⏱ DESIGN STAMINA HYPOTHESIS No design

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⏱ DESIGN STAMINA HYPOTHESIS No design Good design

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⏱ DESIGN STAMINA HYPOTHESIS No design Good design

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⏱ DESIGN STAMINA HYPOTHESIS No design Good design Design payoff line

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Object-oriented design

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The gap.

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Haskell

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Haskell

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Haskell

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Real-world Functional Ruby Southeast Ruby 2017 Tim Riley // @timriley

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FP is hot AF

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App as series of transformations

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Request → [*] → [*] → Response

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App as series of transformations

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App as series of functions

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Functional objects

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class ImportProducts def call(feed) import_from(feed) end end

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class ImportProducts def call(feed) import_from(feed) end end

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class ImportProducts def call(feed) import_from(feed) end end

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class ImportProducts def call(feed) import_from(feed) end end

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Separate data from behaviour

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Immutable

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class ImportProducts def call(feed) end end records = download_feed.(feed) records.each do |attrs| products_repo.create(attrs) end

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class ImportProducts def call(feed) records = download_feed.(feed) records.each do |attrs| products_repo.create(attrs) end end end

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class ImportProducts def call(feed) records = download_feed.(feed) records.each do |attrs| product_repo.create(attrs) end end end

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download_feed: product_repo:

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class ImportProducts attr_reader :download_feed attr_reader :products_repo def initialize(download_feed:, product_repo:) @download_feed = download_feed @products_repo = products_repo end def call(feed) # ... end end

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class ImportProducts attr_reader :download_feed attr_reader :product_repo def initialize(download_feed:, product_repo:) @download_feed = download_feed @product_repo = product_repo end def call(feed) # ... end end

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# Initialize once import = ImportProducts.new( download_feed: download, product_repo: repo, ) # Reuse many times import.(:books_feed) import.(:dvds_feed)

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# Initialize once import = ImportProducts.new( download_feed: download, product_repo: repo, ) # Call many times import.(book_feed) import.(film_feed)

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Feeds::Create Feeds::Update Feeds::Delete Products::Update

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Behaviour

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Data

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Types

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Values

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class Product attr_reader :title, :isbn def initialize(**attrs) @title = attrs[:title] @isbn = attrs[:isbn] end def slug "#{to_slug(title)}-#{isbn}" end end

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class Product attr_reader :title, :isbn def initialize(**attrs) @title = attrs[:title] @isbn = attrs[:isbn] end def slug "#{to_slug(title)}-#{isbn}" end end

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Values objects are first-class

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Values & Functions

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Values Functions Hold data Operate on data

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Values Functions Hold data Operate on data

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Values Functions Hold data Operate on data Inert Active

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Values Functions Hold data Operate on data Inert Active Content Pipeline

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Functional design

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Functional, object-oriented design

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Functional Ruby yields better
 object-oriented Ruby!

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RSpec.describe ImportProducts

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download_feed product_repo

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let(:download) { double(:download) } let(:repo) { double(:repo) }

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subject(:import) { ImportProducts.new( download_feed: download, product_repo: repo, ) }

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let(:feed) { Feed.new(…) } before do allow(download_feed) .to receive(:call) .with(feed) .and_return(books_data) end

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let(:feed) { Feed.new(…) } before do allow(download) .to receive(:call) .with(feed) .and_return(BOOKS_DATA) end

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it "creates the products" do expect(repo) .to receive(:create).with(title: "…") import.(feed) end

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Import
 Products download_feed product_repo

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Dependencies

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App as graph

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Good design makes change easier

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Functional design makes change easier

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Real developers hate him! He’s idealistic He’s making too many .rb files He found a #method to build better apps. Learn the one WEIRD trick to his stunning results! GET FUNCTIONAL NOW

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A real-world functional Ruby ecosystem

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dry-rb

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Dependency management

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dry-system & dry-auto_inject

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# lib/my_app/import_products.rb MyApp::Container[“import_products"] #

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# lib/my_app/import_products.rb MyApp::Container["import_products"] #

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class ImportProducts include MyApp::Import[ "products.download_feed", "product_repo", ] def call(feed) # ... end end

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# lib/my_app/import_products.rb MyApp::Container["import_products"] #

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# lib/my_app/import_products.rb MyApp::Container["import_products"] # product_repo=#>

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ImportProducts.new( download_feed: double(:download) ) # product_repo=#>

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ImportProducts.new( download_feed: double(:download) ) # product_repo=#>

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Result handling

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dry-monads & dry-matcher

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# age, or nil Maybe(age) # successful import results Right(imported_products)

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# age, or nil Maybe(age) Maybe(33) => Some(33) # successful import results Right(imported_products)

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# age, or nil Maybe(age) Maybe(33) => Some(33) Maybe(nil) => None

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# Successful import result Right(imported_products)

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import_products.() do |m| m.success do |imported_products| # … end m.failure do |error| # … end end

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Data & types

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dry-validation

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Dry::Validation.Schema do required(:name).filled required(:url).filled(format?: /…/) required(:active).filled(:bool?) end

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dry-types & dry-struct

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ISBN = Strict::String .constrained(format: /…/)

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class Product < Dry::Struct attribute :title, Types::Strict::String attribute :isbn, Types::ISBN end

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View rendering

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dry-view

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expose :product do |slug:| product_repo.by_slug(slug) end

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HTTP & routing

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dry-web-roda

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$ dry-web-roda new my_app

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. ├── Gemfile ├── README.md ├── Rakefile ├── apps │ └── main │ ├── lib │ │ └── main │ │ └── views │ │ └── welcome.rb │ ├── system │ │ ├── boot │ │ │ └── view.rb │ │ ├── boot.rb │ │ └── main │ │ ├── application.rb │ │ ├── container.rb │ │ ├── import.rb │ │ ├── transactions.rb │ │ ├── view_context.rb │ │ └── view_controller.rb

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│ │ └── relations │ └── types.rb ├── log ├── spec │ ├── app_helper.rb │ ├── db_helper.rb │ ├── spec_helper.rb │ └── support │ ├── db │ │ └── test_factories.rb │ └── test_helpers.rb └── system ├── blog │ ├── application.rb │ ├── container.rb │ ├── import.rb │ └── settings.rb ├── boot │ └── rom.rb └── boot.rb 28 directories, 37 files

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Persistence

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rom-rb

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Dependency management Result handling Data validation & types Views Routing & HTTP Database persistence

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A functional Ruby movement

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hanami

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RailsClub 2017 // @jodosha Functional Web with Hanami

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Ruby is ready

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There is nothing more powerful than an idea whose time has come. — Victor Hugo

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Bridging the gap for Ruby

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Real-world Functional Ruby

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FP + OO = Win!

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FP + OO + Community = Win!

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Functional Ruby is supported

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Functional Ruby is practical

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Functional Ruby is worth a try!

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dry-rb/dry-web-blog

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Thank you! @timriley dry-rb/dry-web-blog bit.ly/se-functional-ruby