Atlanta Ruby Meetup Group: ActiveRecord objects tend to become got objects in our apps. This is because we have forgotten a lot of design and OOP. This is a re-discovery of those principles and how they relate to most Rails apps.

1. Moving ActiveRecord
objects to the
boundaries of your
domain
@PatrickDougall
Patrick Dougall
https://github.com/pdougall1

3. Get in the mood

4. Quick Overview
How do I do this!?
What am I doing?!

5. Logic all over
the place!
Models
Views
Controllers
AR Models
First thing I learned

6. Fat Models / Skinny Controllers
AR Models
Views
Controllers

7. Fat Models / Skinny ControllersSo now you say Domain?
AR Models
Views
Controllers
AR Models
Views
Controllers
AR Models
Views
Controllers
Domain

8. Ok, so what is domain?

9. Ok, so what is domain?

10. The work that this application needs to do
for the domain you’re working with.
• Involves calculations based on input and
stored data
• Validation of any data that comes in from the
presentation layer
• figuring out what data source logic to
dispatch.
Ok, so what is domain?

11. We’ll practice a little
1. AR objects go into an AR directory
2. associations are ok, but only one level deep
(through only one joins table)
3. NO OTHER METHODS
But I have no self control!
we’ll have rules

12. Overview of data model

13. The work that this application needs to do
for the domain you’re working with.
• Involves calculations based on input and
stored data
• Validation of any data that comes in from the
presentation layer
• figuring out what data source logic to
dispatch.
Ok, so what is domain?
query object

14. @projects = Project.where(active: true)
def index
end
Active Projects
class Project < ActiveRecord::Base
has_many :project_user_roles
has_many :users, through: :project_user_roles
has_many :operations
endscope :active, -> { where(active: true) }
@projects = Project.active

15. def index
end
Active Projects
@projects = ActiveProjects.new
class ActiveProjects < SimpleDelegator
def initialize(project_factory: AR::Project)
super project_factory.where(active: true)
end
end

16. But it often things are a
little different

17. Need a user page
SELECT "users".*
FROM "users"
WHERE "users"."id" = 1
module AR
class User < ActiveRecord::Base
end
end
def show
@user = AR::User.find(params[:id])
end

18. SELECT "projects".*
FROM "projects"
INNER JOIN "project_user_roles"
ON "projects"."id" =
"project_user_roles"."project_id"
WHERE "project_user_roles"."user_id" = 1
Also a projects list
def show
@user = AR::User.find(params[:id])@projects = @user.projects
end
has_many :project_user_roles
has_many :projects, through: :project_user_roles
module AR
class User < ActiveRecord::Base
end
end

19. SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" = "projects"."id"
INNER JOIN "users"
ON "users"."id" = "project_user_roles"."user_id"
WHERE "users"."id" = 1
Also an operations list
def show
@user = AR::User.find(params[:id])
@projects = @user.projects
end @operations = @user.operations
has_many :project_user_roles
has_many :projects, through: :project_user_roles
has_many :operations, through: :projects,
source: :operations

20. SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" =
"projects"."id"
WHERE "project_user_roles"."user_id" = 1
def get_operations_scope(user)
@operation_scope
.joins(project: :project_user_roles)
.where(project_user_roles: { user_id: user.id })
end
def get_operations_scope(user)
@operation_scope
.joins(project: :project_user_roles)
.where(project_user_roles: { user_id: user.id })
end
module Query
class UserOperations < SimpleDelegator
def initialize(user, operation_scope: AR::Operation)
@operation_scope = operation_scope
super get_operations_scope(user)
end
end
end
Need an operations list
def show
@user = AR::User.find(params[:id])
@projects = @user.projects
end@operations = UserOperations.new(@user)

21. def show
@user = AR::User.find(params[:id])
@projects = @user.projects
end
@operations = UserOperations.new(@user)
operations listNeed an
def get_operations_scope(user)
@operation_scope
.joins(project: :project_user_roles)
.where(project_user_roles: { user_id: user.id })
end

22. operations listNeed an
SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" =
"projects"."id"
WHERE "project_user_roles"."user_id" = 1
SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" =
"projects"."id"
INNER JOIN "roles"
ON "roles"."id" = "project_user_roles"."role_id"
WHERE "project_user_roles"."user_id" = 1
AND "roles"."name" = "admin

23. operations list
def show
@user = AR::User.find(params[:id])
@projects = @user.projects
end
@operations = UserOperations.new(@user)
def get_operations_scope(user)
@operation_scope
.joins(project: :project_user_roles)
.where(project_user_roles: { user_id: user.id })
Need anactive
end .where(projects: { active: true })

24. .where(projects: { active: true })
.joins(project: :project_user_roles)
.where(roles: { name: “admin” })
def get_operations_scope(user)
@operation_scope
end
.joins(operation: { project: {
project_user_roles: :role
}})
.where(project_user_roles: { user_id: user.id })
SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" =
"projects"."id"
INNER JOIN "roles"
ON "roles"."id" = "project_user_roles"."role_id"
WHERE "project_user_roles"."user_id" = 1
AND "roles"."name" = "admin
def show
@user = AR::User.find(params[:id])
@projects = @user.projects
end
@operations = UserOperations.new(@user)
operations listNeed an active for admin

25. def get_operations_scope(user)
@operation_scope
.joins(project: {
project_user_roles: :role
})
.where(project_user_roles: { user_id: user.id })
.where(roles: { name: "admin" })
end
SELECT "operations".*
FROM "operations"
INNER JOIN "projects"
ON "projects"."id" = "operations"."project_id"
INNER JOIN "project_user_roles"
ON "project_user_roles"."project_id" =
"projects"."id"
INNER JOIN "roles"
ON "roles"."id" = "project_user_roles"."role_id"
WHERE "project_user_roles"."user_id" = 1
AND "roles"."name" = "admin

26. The work that this application needs to do
for the domain you’re working with.
• Involves calculations based on input and
stored data
• Validation of any data that comes in from the
presentation layer
• figuring out what data source logic to
dispatch.
Ok, so what is domain?
query object
form object

27. Need a new User
def new
@user = AR::User.new
end
class User < ActiveRecord::Base
endvalidates_presence_of :first_name,
:last_name,
:email

28. Need a new User
def new
end
@user = Form::User.new
class User
include ActiveModel::Model
validates_presence_of :first_name,
:last_name,
:email
end

29. The work that this application needs to do
for the domain you’re working with.
• Involves calculations based on input and
stored data
• Validation of any data that comes in from the
presentation layer
• figuring out what data source logic to
dispatch.
Ok, so what is domain?
query object
form object
PORO ?

30. • Less likely to create god object
• Naturally ends up in their own objects
• Easier to understand our objects
Why is this good?

31. 1. OOP 2015 Keynote - Robert C. Martin ("Uncle Bob"): Agility and Architecture
• https://www.youtube.com/watch?v=0oGpWmS0aYQ
2. Martin Fowler: Patterns of Enterprise Architecture
• http://martinfowler.com/books/eaa.html
References