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The Magic of Rails
exploring the principles & techniques
behind the framework
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Eileen M. Uchitelle
eileencodes.com
@eileencodes
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The Magic of Rails
exploring the principles & techniques
behind the framework
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What is
Ruby on Rails?
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Rails is
modular, but
not fractured
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Rails is
designed to
have agnostic
interfaces
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Rails is
extracted from
applications
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Rails is
made of
simple and
aesthetic APIs
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Rails is
a framework
that takes on
complexity to
empower you
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How Rails components
are structured
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RUBY ON RAILS
Active Record
Active Support
Active Model
Active Job
Active Storage
Action Mailer
Action Pack Action View
Action Cable
Action Text
Action Mailbox
Railties
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Naming Convention
Active vs Action
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Active Record
Active Support
Active Model
Active Job
Active Storage
BACKEND
NAMING CONVENTION
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USER FACING
Active Record
Active Support
Active Model
Active Job
Active Storage
BACKEND
NAMING CONVENTION
Action Mailer
Action Pack
Action View
Action Cable
Action Text
Action Mailbox
USER FACING
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Active Record
Active Support
Active Model
Active Job
Active Storage
Action Mailer
Action Pack
Action View
Action Cable
Action Text
Action Mailbox
BACKEND USER FACING
Railties
GLUE
NAMING CONVENTION
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Architecture & Patterns
of Rails components
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Architecture & Patterns
the role of Railties
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👩💻
Application
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👩💻
Application Register hooks
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👩💻
Application Register hooks Load components
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👩💻
Application Register hooks Load components Run hooks
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# railtie.rb
initializer "initializer.name" do
# do something at initialization
end
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# railties/lib/rails/application.rb
def initializer(name, opts = {}, &block)
self.class.initializer(name, opts, &block)
end
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# railtie.rb
initializer "initializer.name" do |app|
app.do_something
app.config.do_something
end
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# railtie.rb
initializer "initializer.name" do
ActiveSupport.on_load(:active_record) do
# do something at initialization
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.initialize_database" do
ActiveSupport.on_load(:active_record) do
self.configurations =
Rails.application.config.database_configuration
establish_connection
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.initialize_database" do
ActiveSupport.on_load(:active_record) do
self.configurations =
Rails.application.config.database_configuration
establish_connection
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.initialize_database" do
ActiveSupport.on_load(:active_record) do
self.configurations =
Rails.application.config.database_configuration
establish_connection
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.log_runtime" do
require "active_record/railties/controller_runtime"
ActiveSupport.on_load(:action_controller) do
include ActiveRecord::Railties::ControllerRuntime
end
require "active_record/railties/job_runtime"
ActiveSupport.on_load(:active_job) do
include ActiveRecord::Railties::JobRuntime
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.log_runtime" do
require "active_record/railties/controller_runtime"
ActiveSupport.on_load(:action_controller) do
include ActiveRecord::Railties::ControllerRuntime
end
require "active_record/railties/job_runtime"
ActiveSupport.on_load(:active_job) do
include ActiveRecord::Railties::JobRuntime
end
end
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# activerecord/lib/active_record/railtie.rb
initializer "active_record.log_runtime" do
require "active_record/railties/controller_runtime"
ActiveSupport.on_load(:action_controller) do
include ActiveRecord::Railties::ControllerRuntime
end
require "active_record/railties/job_runtime"
ActiveSupport.on_load(:active_job) do
include ActiveRecord::Railties::JobRuntime
end
end
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# activejob/lib/active_job/railtie.rb
initializer "active_model.deprecator",
before: :load_environment_config do |app|
app.deprecators[:active_model] =
ActiveModel.deprecator
end
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# activejob/lib/active_job/railtie.rb
initializer "active_model.deprecator",
before: :load_environment_config do |app|
app.deprecators[:active_model] =
ActiveModel.deprecator
end
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• Railties are the core of
the framework
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• Railties are the core of
the framework
• Railties control load
order and when hooks
should be run
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• Railties are the core of
the framework
• Railties control load
order and when hooks
should be run
• Enables components to
work together without
adding dependencies
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Architecture & Patterns
Agnostic interfaces
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if connection.is_a?(PostgresqlAdapter)
# ...
elsif connection.is_a?(Mysql2Adapter)
# ...
elsif connection.is_a?(TrilogyAdapter)
# ...
elsif connection.is_?(Sqlite3Adapter)
# ...
else
# ...
end
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if connection.is_a?(PostgresqlAdapter)
# ...
elsif connection.is_a?(Mysql2Adapter)
# ...
elsif connection.is_a?(TrilogyAdapter)
# ...
elsif connection.is_?(Sqlite3Adapter)
# ...
else
# ...
end
❌
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module ActiveRecord
module ConnectionAdapters
class AbstractAdapter
# define interface
end
end
end
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module ActiveRecord
module ConnectionAdapters
class AbstractAdapter
# define interface
end
end
end
module ActiveRecord
module ConnectionAdapters
class PostgresqlAdapter < AbstractAdapter
# inherit or redefine interface
end
end
end
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connection.supports_foreign_keys?
=> true
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class AbstractAdapter
def supports_foreign_keys?
false
end
end
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class AbstractAdapter
def supports_foreign_keys?
false
end
end
class PostgresqlAdapter < AbstractAdapter
def supports_foreign_keys?
true
end
end
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# activestorage/lib/active_storage/service.rb
module ActiveStorage
class Service
def delete(key)
raise NotImplementedError
end
end
end
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# activestorage/lib/active_storage/service/gcs_service.rb
class ActiveStorage
class Service::GCSService < Service
def delete(key)
instrument :delete, key: key do
file_for(key).delete
rescue Google::Cloud::NotFoundError
# Ignore files already deleted
end
end
end
end
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@service.delete(key)
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• Consistent interface for
all supported libraries
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• Consistent interface for
all supported libraries
• Simpli
fi
es Rails code to
avoid using `is_a?`
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• Consistent interface for
all supported libraries
• Simpli
fi
es Rails code to
avoid using `is_a?`
• Makes it easy for apps to
swap out adapters /
services
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• Consistent interface for
all supported libraries
• Simpli
fi
es Rails code to
avoid using `is_a?`
• Makes it easy for apps to
swap out adapters /
services
• Lowers the maintenance
burden
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Architecture & Patterns
Metaprogramming
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class Post < ApplicationRecord
has_many :comments
end
class Comment < ApplicationRecord
belongs_to :post
end
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post = Post.first
post.comments
=> [#,
#]
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post = Post.first
post.method(:comments).source_location
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post = Post.first
post.method(:comments).source_location
=> ["rails/activerecord/lib/
active_record/associations/builder/
association.rb", 103]
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_readers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}
association(:#{name}).reader
end
CODE
end
end
end
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_readers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}
association(:#{name}).reader
end
CODE
end
end
end
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_readers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}
association(:#{name}).reader
end
CODE
end
end
end
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Post::GeneratedAssociationMethods
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_readers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}
association(:#{name}).reader
end
CODE
end
end
end
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_writers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}=(value)
association(:#{name}).writer(value)
end
CODE
end
end
end
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# activerecord/lib/active_record/associations/builder/
association.rb
class ActiveRecord::Associations::Builder
class Association
def self.define_writers(mixin, name)
mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
def #{name}=(value)
association(:#{name}).writer(value)
end
CODE
end
end
end
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• Powerful tool that
enables us to build
beautiful, simple APIs
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• Powerful tool that
enables us to build
beautiful, simple APIs
• Hides complexity from
your application
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• Powerful tool that
enables us to build
beautiful, simple APIs
• Hides complexity from
your application
• Where "Rails Magic"
comes from
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Maintaining Rails
Why I work on it
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2010
Introduced
to Rails
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2010
Introduced
to Rails
2011
Big Nerd Ranch
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2010
Introduced
to Rails
2011
Big Nerd Ranch
2014
1st conference
1st contribution
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2010
Introduced
to Rails
2011
Big Nerd Ranch
2014
1st conference
1st contribution
2015
First RailsConf
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2010
Introduced
to Rails
2011
Big Nerd Ranch
2014
1st conference
1st contribution
2015
First RailsConf
2017
Join Rails Core
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2010
Introduced
to Rails
2011
Big Nerd Ranch
2014
1st conference
1st contribution
2015
First RailsConf
2017
Join Rails Core
2023
Rails is 20!
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I work on Rails to
advance the
framework
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I work on Rails to
ensure applications
can stay on Rails
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I work on Rails to
build a stronger
community
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I work on Rails to
have an impact
on the future
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Rails is so much more
than just a framework
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Rails is
inspiring
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Rails is
empowering
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Rails is
imperfect
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Rails is
the applications we build
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Rails is
the team behind it
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Rails is
the community
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Rails is magic
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Thank You!
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Eileen M. Uchitelle
eileencodes.com
@eileencodes
Senior Staff Engineer @ Shopify
Rails Core Team