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Refinements in Ruby twitter.com/kddeisz

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new

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twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new c.foo # prints "C#foo in M"

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Usage

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No content

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Law of Demeter

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Law of Demeter Common interfaces

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Law of Demeter Common interfaces Local monkey-patches

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twitter.com/kddeisz Refinements in Ruby class Organization < ApplicationRecord has_many :events has_many :users end class Event < ApplicationRecord belongs_to :host, class_name: 'User' belongs_to :organization has_many :rsvps end class Rsvp < ApplicationRecord belongs_to :event belongs_to :user end class User < ApplicationRecord belongs_to :organization has_many :hosted_events, foreign_key: :host_id, class_name: 'Event' has_many :rsvps end

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Law of Demeter

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Law of Demeter Only talk to your friends

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? !event.invite_only? || rsvp.status_was == 'invited' end end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? event.allowed_rsvp?(status_was) end end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Module.new { refine Event do def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end } belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Module.new { refine Event do def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end } belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << to_row(event) end end end private def to_row(event) [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end class Event < ApplicationRecord def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob using Module.new { refine Event do def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end } def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end class Event < ApplicationRecord def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end

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twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob using Module.new { refine Event do def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end } def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end

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Common interfaces

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_organization? superuser? end end

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_event?(event) event.host == self end def can_admin_organization? superuser? end end

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_event?(event) event.host == self end def can_admin_organization? superuser? end def can_admin_rsvp?(rsvp) rsvp.user == self || can_admin_event?(rsvp.event) end end

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin?(record) case record when Event record.host == self when Organization superuser? when Rsvp record.user == self || can_admin?(record.event) else raise ArgumentError end end end

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin?(record) record.admin?(self) end end class Event < ApplicationRecord def admin?(user) host == user end end class Organization < ApplicationRecord def admin?(user) user.superuser? end end class Rsvp < ApplicationRecord def admin?(other) user == other || event.admin?(other) end end

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twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(self) ennd

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twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd

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twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd class User < ApplicationRecord delegate :can_admin?, to: :admin_rules def admin_rules AdminRules.new(self) end end

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twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd class User < ApplicationRecord delegate :can_admin?, to: :admin_rules def admin_rules AdminRules.new(self) end end

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Local monkey-patches

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twitter.com/kddeisz Refinements in Ruby class Hash def except(*keys) slice(*self.keys - keys) end end class UsersController < ApplicationController def update if @user.update(params[:user].except(:admin)) render @user, status: :success else render @user.errors, status: :unprocessable_entity end end end

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twitter.com/kddeisz Refinements in Ruby class UsersController < ApplicationController using Module.new { refine Hash do def except(*keys) slice(*self.keys - keys) end end } def update if @user.update(params[:user].except(:admin)) render @user, status: :success else render @user.errors, status: :unprocessable_entity end end end

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twitter.com/kddeisz Refinements in Ruby class Object def blank? respond_to?(:empty?) ? !!empty? : !self end end class NilClass def blank? true end end class FalseClass def blank? true end end class TrueClass def blank? false end end class Array alias_method :blank?, :empty? end class Hash alias_method :blank?, :empty? end class String def blank? empty? || BLANK_RE.match?(self) end end

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twitter.com/kddeisz Refinements in Ruby module Blank refine Object do def blank? respond_to?(:empty?) ? !!empty? : !self end end refine NilClass do def blank? true end end refine FalseClass do def blank? true end end refine TrueClass do def blank? false end ennd module Blank refine Array do alias_method :blank?, :empty? end refine Hash do alias_method :blank?, :empty? end refine String do def blank? empty? || BLANK_RE.match?(self) end end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord before_validation do self.message = message.blank? ? nil : message end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Blank before_validation do self.message = message.blank? ? nil : message end end

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twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using ActiveSupport::StringExtensions before_validation do self.message = message.blank? ? nil : message end end

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Conclusions

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Code that changes together should live together

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Refinements can move code out of class definitions and into where it is used

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Use refinements to organize your code so developers don’t have to open so many files to make changes

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Refinements in Ruby twitter.com/kddeisz