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Vladimir Dementyev
Evil Martians
RAILS AS A PIECE
OF BIRTHDAY CAKE
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guides.rubyonrails.org
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–Application Programming in
Smalltalk-80 (TM), Steve Burbeck, 1987
“In the MVC paradigm the user input, the
modeling of the external world, and the visual
feedback to the user are explicitly separated
and handled by three types of object, each
specialized for its task.”
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The model class
concerns itself only
with the application's
state and logic
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The view class
concerns itself only
with creating the user
interface
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The controller class is
occupied solely with
translating user input
into updates that it
passes to the model
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Rails vs MVC
Model
View
Controller
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Rails vs MVC
Model
View
Controller
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Rails vs MVC
View
Controller
Model
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Rails vs MVC
View
Controller
Model
Un-separation of
concerns
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MVC cake
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Mature MVC cake
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Beyond MVC cake
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github.com/palkan
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github.com/palkan
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evilmartians.com/events
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Layers on Rails
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Rails Way
Request
Response
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Rails Way
Model
Controller View
Request
Response
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Extended Rails Way
Model
Controller View
?
Request
Response
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Maintainability
Readability
Testability
Coupling
Cohesion
Extensibility
Flexibility Complexity
Reusability
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Bad abstractions Good abstractions
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Abstractions
on Rails
Railroad at Murnau, Wassily Kandinsky
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Abstraction layer for Rails cake
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Abstraction
Generalization
Encapsulation
Loose Coupling
Testability Centralization
Simplification Single Responsibility
Reusability
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Rails Abstraction
Generalization
Encapsulation
Loose Coupling
Testability Centralization
Simplification
Single Responsibility
Reusability
Conventions
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Abstraction layer for Rails cake
1. Rails conventions Learn how Rails work, re-use
patterns and building blocks.
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Layered Architecture
Presentation
Application
Domain
Infrastructure
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Layered Architecture
Presentation
Application
Domain
Infrastructure
!
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Layered Architecture
Presentation
Application
Domain
Infrastructure
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Layered Architecture
Presentation
Application
Domain
Infrastructure
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Controllers
Presentation
Channels
Views
Application Jobs
Mailers
Domain
Infrastructure
Models
Adapters (DB, mail)
API clients
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class Authenticator
def call(request)
auth_header = request.headers["Authorization"]
raise "Missing auth header" unless auth_header
token = auth_header.split(" ").last
raise "No token found" unless token
JWT.decode(
token,
Rails.application.secrets.secret_key_base
).then do
User.find(_1["user_id"]) if _1["user_id"]
end
end
end
Layer: ?
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class Authenticator
def call(request)
auth_header = request.headers["Authorization"]
raise "Missing auth header" unless auth_header
token = auth_header.split(" ").last
raise "No token found" unless token
JWT.decode(
token,
Rails.application.secrets.secret_key_base
).then do
User.find(_1["user_id"]) if _1["user_id"]
end
end
end
Presentation
Layer: Presentation
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class Authenticator
def call(request)
auth_header = request.headers["Authorization"]
raise "Missing auth header" unless auth_header
token = auth_header.split(" ").last
raise "No token found" unless token
JWT.decode(
token,
Rails.application.secrets.secret_key_base
).then do
User.find(_1["user_id"]) if _1["user_id"]
end
end
end
Presentation
Infrastructure
Layer: Presentation ???
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class Authenticator
def call(token)
raise "No token found" unless token
JWT.decode(
token,
Rails.application.secrets.secret_key_base
).then do
User.find(_1["user_id"]) if _1["user_id"]
end
end
end
Layer: Application
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An object belongs to the highest architecture
layer among all its inputs and dependencies
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Abstraction layer for Rails cake
1. Rails conventions Learn how Rails work, re-use
patterns and building blocks.
2. Layered architecture ideas Identify the target arch. layer;
avoid mixing too many layers.
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How to choose new abstractions?
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How to choose new extract abstractions?
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Abstraction layer for Rails cake
1. Rails conventions Learn how Rails work, re-use
patterns and building blocks.
2. Layered architecture ideas Identify the target arch. layer;
avoid mixing too many layers.
3. Сodebase extracts, no
artificial concepts
Perform complexity analysis,
analyze and extract abstractions.
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Extraction
Time
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class GithooksController < ApplicationController
def create
event = JSON.parse(request.raw_post, symbolize_names: true)
login = event.dig(:issue, :user, :login) ||
event.dig(:pull_request, :user, :login)
User.find_by(gh_id: login)
&.handle_github_event(event) if login
head :ok
end
end
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Case #1: Models vs. webhooks
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class User < ApplicationRecord
def handle_github_event(event)
case event
in type: "issue", action: "opened",
issue: {user: {login:}, title:, body:}
issues.create!(title:, body:)
in type: "pull_request", action: "opened",
pull_request: {
user: {login:}, base: {label:}, title:, body:
}
pull_requests.create!(title:, body:, branch:)
end
end
end
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class User < ApplicationRecord
def handle_github_event(event)
case event
in type: "issue", action: "opened",
issue: {user: {login:}, title:, body:}
issues.create!(title:, body:)
in type: "pull_request", action: "opened",
pull_request: {
user: {login:}, base: {label:}, title:, body:
}
pull_requests.create!(title:, body:, branch:)
end
end
end
Hash originated in
the outer world
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class GitHubEvent
def self.parse(raw_event)
parsed = JSON.parse(raw_event, symbolize_names: true)
case parsed[:type]
when "issue"
Issue.new(
# ...
)
when "pull_request"
PR.new(
# ...
)
end
rescue JSON::ParserError
nil
end
Issue = Data.define(:user_id, :action, :title, :body)
PR = Data.define(:user_id, :action, :title, :body, :branch)
end
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class GithooksController < ApplicationController
def create
event = GitHubEvent.parse(request.raw_post)
User.find_by(gh_id: event.user_id)
&.handle_github_event(event) if event
head :ok
end
end
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class User < ApplicationRecord
def handle_github_event(event)
case event
in GitHubEvent::Issue[action: "opened", title:, body:]
issues.create!(title:, body:)
in GitHubEvent::PR[
action: "opened", title:, body:, branch:
]
pull_requests.create!(title:, body:, branch:)
end
end
end
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Maintainability "
— Controller: not ad-hoc hacks, less churn
— Model: no knowledge of the outer world
— Webhook payload access is encapsulated
and localized
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Should a model be responsible for handling
webhooks at all?
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Controllers
Presentation
Channels
Views
Application Jobs
Mailers
Domain
Infrastructure
Models
Adapters (DB, mail)
API clients
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Controllers
Presentation
Channels
Views
Application Jobs
Mailers
Domain
Infrastructure
Models
Adapters (DB, mail)
Service Objects
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Service Objects
— Pseudo abstraction layer (generalization,
consistency)
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Service Objects
— Pseudo abstraction layer (generalization,
consistency)
— "app/services"—bag of random objects
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Service Objects
— Pseudo abstraction layer (generalization,
consistency)
— "app/services"—bag of random objects
—Intermediate stage until the final
abstraction emerges
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Service objects ~ waiting room
sms_sender.rb
rss_service.rb
remind_user.rb
auth_service.rb post/publish.rb
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To "app/services" or not to
"app/services"?
— Don't start early with abstractions →
better generalization requires a bit of
aging
— Don't overcrowd "app/services"
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class GithooksController < ApplicationController
def create
event = GitHubEvent.parse(request.raw_post)
GithubEventHandler.call(event) if event
head :ok
end
end
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class GithubEventHandler
def self.call(event)
user = User.find_by(gh_id: event.user_id)
return false unless user
case event
in GitHubEvent::Issue[action: "opened", title:, body:]
user.issues.create!(title:, body:)
in GitHubEvent::PR[
action: "opened", title:, body:, branch:
]
user.pull_requests.create!(title:, body:, branch:)
else
# ignore unknown events
end
true
end
end
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Case #2: Models vs. forms
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class User < ApplicationRecord
attribute :should_send_invitation, :boolean
after_commit :send_invitation, if: :should_send_invitation,
on: :create
def send_invitation
UserMailer.invite(self).deliver_later
end
end
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class User < ApplicationRecord
attribute :should_send_invitation, :boolean
after_commit :send_invitation, if: :should_send_invitation,
on: :create
def send_invitation
UserMailer.invite(self).deliver_later
end
end
Layered Arch: Sending emails from models? Is it even legal #
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class User < ApplicationRecord
attribute :should_send_invitation, :boolean
after_commit :send_invitation, if: :should_send_invitation,
on: :create
def send_invitation
UserMailer.invite(self).deliver_later
end
end
Layered Arch: Sending emails from models? Is it even legal #
Context-specific information now a part of the domain model
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class User < ApplicationRecord
attribute :should_send_invitation, :boolean
after_commit :send_invitation, if: :should_send_invitation,
on: :create
def send_invitation
UserMailer.invite(self).deliver_later
end
end
>= Application Layer
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class InvitationsController < ApplicationController
def create
@user = User.new(params.require(:user).permit(:email))
@user.should_send_invitation = true
if @user.save
if params[:send_copy] == "1"
UserMailer.invite_copy(current_user, @user)
.deliver_later
end
redirect_to root_path, notice: "Invited!"
else
render :new
end
end
end
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class InvitationsController < ApplicationController
def create
@user = User.new(params.require(:user).permit(:email))
@user.should_send_invitation = true
if @user.save
if params[:send_copy] == "1"
UserMailer.invite_copy(current_user, @user)
.deliver_later
end
redirect_to root_path, notice: "Invited!"
else
render :new
end
end
end
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Leaking abstraction $
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Where can we localize
the invitation form logic?
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Jobs
Service Objects
Application
Mailers
Domain
Infrastructure
Models
DB / API / etc
Controllers
Presentation
Channels
Views
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Jobs
Service Objects
Application
Mailers
Domain Models
Form objects
Controllers
Presentation
Channels
Views
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class UserInvitationForm
attr_reader :user, :send_copy, :sender
def initialize(email, send_copy: false, sender: nil)
@user = User.new(email:)
@send_copy = send_copy.in?(%w[1 t true])
@sender = sender
end
def save
return false unless user.valid?
user.save!
deliver_notifications!
true
end
def deliver_notifications!
UserMailer.invite(user).deliver_later
if send_copy
UserMailer.invite_copy(sender, user).deliver_later
end
end
end
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class UserInvitationForm
attr_reader :user, :send_copy, :sender
def initialize(email, send_copy: false, sender: nil)
@user = User.new(email:)
@send_copy = send_copy.in?(%w[1 t true])
@sender = sender
end
def save
return false unless user.valid?
user.save!
deliver_notifications!
true
end
def deliver_notifications!
UserMailer.invite(user).deliver_later
if send_copy
UserMailer.invite_copy(sender, user).deliver_later
end
end
end
Manual type-casting
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class InvitationsController < ApplicationController
def create
form = UserInvitationForm.new(
params.require(:user).permit(:email)[:email],
params[:send_copy],
current_user
)
if form.save
redirect_to root_path, notice: "Invited!"
else
@user = form.user
render :new
end
end
end
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class InvitationsController < ApplicationController
def create
form = UserInvitationForm.new(
params.require(:user).permit(:email)[:email],
params[:send_copy],
current_user
)
if form.save
redirect_to root_path, notice: "Invited!"
else
@user = form.user
render :new
end
end
end
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Two sets of params
Hack to re-use templates +
leaking internals
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class InvitationsController < ApplicationController
def create
form = UserInvitationForm.new(
params.require(:user).permit(:email)[:email],
params[:send_copy],
current_user
)
if form.save
redirect_to root_path, notice: "Invited!"
else
@user = form.user
render :new
end
end
end
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Two sets of params
Hack to re-use templates +
leaking internals
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— Type casting, validations
— Trigger side actions on successful
submission
— Compatibility with the view layer
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Form object → Rails abstraction
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Form object → Rails abstraction
— Type casting, validations → ActiveModel::API
+ ActiveModel::Attributes
— Trigger side actions on successful
submission → ActiveSupport::Callbacks
— Compatibility with the view layer →
ActiveModel::Name + conventions
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class InvitationForm < ApplicationForm
attribute :email
attribute :send_copy, :boolean
attr_accessor :sender
validates :email, presence: true
after_commit :deliver_invitation
after_commit :deliver_invitation_copy, if: :send_copy
def submit!
@user = User.new(email:)
@user.save!
end
def deliver_invitation
UserMailer.invite(@user).deliver_later
end
def deliver_invitation_copy
UserMailer.invite_copy(sender, @user).deliver_later if sender
end
end
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class InvitationForm < ApplicationForm
attribute :email
attribute :send_copy, :boolean
attr_accessor :sender
validates :email, presence: true
after_commit :deliver_invitation
after_commit :deliver_invitation_copy, if: :send_copy
def submit!
@user = User.new(email:)
@user.save!
end
def deliver_invitation
UserMailer.invite(@user).deliver_later
end
def deliver_invitation_copy
UserMailer.invite_copy(sender, @user).deliver_later if sender
end
end
Form fields (w/types)
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class InvitationForm < ApplicationForm
attribute :email
attribute :send_copy, :boolean
attr_accessor :sender
validates :email, presence: true
after_commit :deliver_invitation
after_commit :deliver_invitation_copy, if: :send_copy
def submit!
@user = User.new(email:)
@user.save!
end
def deliver_invitation
UserMailer.invite(@user).deliver_later
end
def deliver_invitation_copy
UserMailer.invite_copy(sender, @user).deliver_later if sender
end
end
Form fields (w/types)
Core logic
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class InvitationForm < ApplicationForm
attribute :email
attribute :send_copy, :boolean
attr_accessor :sender
validates :email, presence: true
after_commit :deliver_invitation
after_commit :deliver_invitation_copy, if: :send_copy
def submit!
@user = User.new(email:)
@user.save!
end
def deliver_invitation
UserMailer.invite(@user).deliver_later
end
def deliver_invitation_copy
UserMailer.invite_copy(sender, @user).deliver_later if sender
end
end
Form fields (w/types)
Core logic
Trigger actions
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class InvitationsController < ApplicationController
def new
@invitation_form = InvitationForm.new
end
def create
@invitation_form = InvitationForm.new(
params.require(:invitation).permit(:email, :send_copy)
)
@invitation_form.sender = current_user
if @invitation_form.save
redirect_to root_path
else
render :new, status: :unprocessable_entity
end
end
end
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<%= form_for(@invitation_form) do |form| %>
<%= form.label :email %>
<%= form.text_field :email %>
<%= form.label :send_copy, "Send me the copy" %>
<%= form.check_box :send_copy %>
<%= form.submit "Invite" %>
<% end %>
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
Callbacks
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
Callbacks
Transaction-awareness
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
Callbacks
Transaction-awareness
Action View compatibility
(InvitationForm → /invitations)
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
Callbacks
Transaction-awareness
Action View compatibility
(InvitationForm → /invitations)
Interface
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class ApplicationForm
include ActiveModel::API
include ActiveModel::Attributes
define_callbacks :save, only: :after
define_callbacks :commit, only: :after
def save
return false unless valid?
with_transaction do
AfterCommitEverywhere.after_commit { run_callbacks(:commit) }
run_callbacks(:save) { submit! }
end
end
def model_name
ActiveModel::Name.new(nil, nil, self.class.name.sub(/Form$/, ""))
end
private
def with_transaction(&) = ApplicationRecord.transaction(&)
def submit!
raise NotImplementedError
end
end
Types and validations
Callbacks
Transaction-awareness
Action View compatibility
Interface
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palkan_tula
palkan
— Type casting, validations ✅
— Trigger side actions on successful submission ✅
— Compatibility with the view layer ✅
— Strong parameters compatibility
— DX (test matchers, generators)
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Form object → Rails abstraction
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79
Abstraction layer for Rails cake
1. Rails conventions Learn how Rails work, re-use
patterns and building blocks.
2. Layered architecture ideas Identify the target arch. layer;
avoid mixing too many layers.
3. Сodebase extracts, no
artificial concepts
Perform complexity analysis,
analyze and extract abstractions.
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79
Abstraction layer for Rails cake
1. Rails conventions Learn how Rails work, re-use
patterns and building blocks.
2. Layered architecture ideas Identify the target arch. layer;
avoid mixing too many layers.
3. Сodebase extracts, no
artificial concepts
Perform complexity analysis,
analyze and extract abstractions.
Feel free to experiment and add ingredients from other
paradigms and ecosystems!
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palkan_tula
palkan
How many layers is enough?
80
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Controllers
Channels
Presentation
Views
Application
Jobs
Presenters
Form objects
Filter objects
Deliveries
Authorization Policies
Event Listeners
Interactors
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Mailers
Domain
Infrastructure
Models
Adapters (DB, mail)
API clients
Deliveries
Notifiers
Interactors
Query objects
Configuration objects
Value objects
Service objects
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The Book
Coming Oct 2023
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@palkan
@palkan_tula
evilmartians.com
@evilmartians
Thanks!