cea392eb96
In case of a polymorphic association there's no automatic inverse_of to assign the inverse record. So to get the record there needs to be a query executed, however, if the query fires within the transaction that's trying to create the associated record, no record can be found. And worse, the nil result is cached on the association so after the transaction commits the record can't be found. That's what happens if touch is enabled on a polymorphic has_one association. Consider a Comment with a commentable association that needs to be touched. For `Comment.create(commentable: Post.new)`, the existing code essentially does `commentable.send(:comment)` within the create transaction for the comment and thus not finding the comment. Now we're purposefully clearing the cache in case we've tried accessing the association within the transaction and found no object. Before: ``` kaspth-imac 2.6.3 ~/code/rails/activerecord master *= ARCONN=postgresql bin/test test/cases/associations/has_one_associations_test.rb -n /commit/ Using postgresql Run options: -n /commit/ --seed 46022 D, [2019-07-19T03:30:37.864537 #96022] DEBUG -- : Chef Load (0.2ms) SELECT "chefs".* FROM "chefs" WHERE "chefs"."employable_id" = $1 AND "chefs"."employable_type" = $2 LIMIT $3 [["employable_id", 1], ["employable_type", "DrinkDesignerWithPolymorphicTouchChef"], ["LIMIT", 1]] D, [2019-07-19T03:30:37.865013 #96022] DEBUG -- : Chef Create (0.2ms) INSERT INTO "chefs" ("employable_id", "employable_type") VALUES ($1, $2) RETURNING "id" [["employable_id", 1], ["employable_type", "DrinkDesignerWithPolymorphicTouchChef"]] D, [2019-07-19T03:30:37.865201 #96022] DEBUG -- : TRANSACTION (0.1ms) RELEASE SAVEPOINT active_record_1 D, [2019-07-19T03:30:37.874136 #96022] DEBUG -- : TRANSACTION (0.1ms) ROLLBACK D, [2019-07-19T03:30:37.874323 #96022] DEBUG -- : TRANSACTION (0.1ms) ROLLBACK F Failure: HasOneAssociationsTest#test_polymorphic_has_one_with_touch_option_on_create_wont_cache_assocation_so_fetching_after_transaction_commit_works [/Users/kaspth/code/rails/activerecord/test/cases/associations/has_one_associations_test.rb:716]: --- expected +++ actual @@ -1 +1 @@ -#<Chef id: 1, employable_id: 1, employable_type: "DrinkDesignerWithPolymorphicTouchChef", department_id: nil, employable_list_type: nil, employable_list_id: nil> +nil ``` After: ``` kaspth-imac 2.6.3 ~/code/rails/activerecord master *= ARCONN=postgresql bin/test test/cases/associations/has_one_associations_test.rb -n /commit/ Using postgresql Run options: -n /commit/ --seed 46022 D, [2019-07-19T03:30:22.479387 #95973] DEBUG -- : Chef Create (0.3ms) INSERT INTO "chefs" ("employable_id", "employable_type") VALUES ($1, $2) RETURNING "id" [["employable_id", 1], ["employable_type", "DrinkDesignerWithPolymorphicTouchChef"]] D, [2019-07-19T03:30:22.479574 #95973] DEBUG -- : TRANSACTION (0.1ms) RELEASE SAVEPOINT active_record_1 D, [2019-07-19T03:30:22.482051 #95973] DEBUG -- : Chef Load (0.1ms) SELECT "chefs".* FROM "chefs" WHERE "chefs"."employable_id" = $1 AND "chefs"."employable_type" = $2 LIMIT $3 [["employable_id", 1], ["employable_type", "DrinkDesignerWithPolymorphicTouchChef"], ["LIMIT", 1]] D, [2019-07-19T03:30:22.482317 #95973] DEBUG -- : TRANSACTION (0.1ms) ROLLBACK D, [2019-07-19T03:30:22.482437 #95973] DEBUG -- : TRANSACTION (0.1ms) ROLLBACK . Finished in 0.088498s, 11.2997 runs/s, 22.5994 assertions/s. 1 runs, 2 assertions, 0 failures, 0 errors, 0 skips ``` Notice the select now fires after the commit. |
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actioncable | ||
actionmailbox | ||
actionmailer | ||
actionpack | ||
actiontext | ||
actionview | ||
activejob | ||
activemodel | ||
activerecord | ||
activestorage | ||
activesupport | ||
ci | ||
guides | ||
railties | ||
tasks | ||
tools | ||
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Brewfile | ||
CODE_OF_CONDUCT.md | ||
CONTRIBUTING.md | ||
Gemfile | ||
Gemfile.lock | ||
MIT-LICENSE | ||
package.json | ||
rails.gemspec | ||
RAILS_VERSION | ||
Rakefile | ||
README.md | ||
RELEASING_RAILS.md | ||
version.rb | ||
yarn.lock |
Welcome to Rails
What's Rails?
Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.
Understanding the MVC pattern is key to understanding Rails. MVC divides your application into three layers: Model, View, and Controller, each with a specific responsibility.
Model layer
The Model layer represents the domain model (such as Account, Product,
Person, Post, etc.) and encapsulates the business logic specific to
your application. In Rails, database-backed model classes are derived from
ActiveRecord::Base
. Active Record allows you to present the data from
database rows as objects and embellish these data objects with business logic
methods.
Although most Rails models are backed by a database, models can also be ordinary
Ruby classes, or Ruby classes that implement a set of interfaces as provided by
the Active Model module.
Controller layer
The Controller layer is responsible for handling incoming HTTP requests and
providing a suitable response. Usually this means returning HTML, but Rails controllers
can also generate XML, JSON, PDFs, mobile-specific views, and more. Controllers load and
manipulate models, and render view templates in order to generate the appropriate HTTP response.
In Rails, incoming requests are routed by Action Dispatch to an appropriate controller, and
controller classes are derived from ActionController::Base
. Action Dispatch and Action Controller
are bundled together in Action Pack.
View layer
The View layer is composed of "templates" that are responsible for providing appropriate representations of your application's resources. Templates can come in a variety of formats, but most view templates are HTML with embedded Ruby code (ERB files). Views are typically rendered to generate a controller response, or to generate the body of an email. In Rails, View generation is handled by Action View.
Frameworks and libraries
Active Record, Active Model, Action Pack, and Action View can each be used independently outside Rails. In addition to that, Rails also comes with Action Mailer, a library to generate and send emails; Action Mailbox, a library to receive emails within a Rails application; Active Job, a framework for declaring jobs and making them run on a variety of queuing backends; Action Cable, a framework to integrate WebSockets with a Rails application; Active Storage, a library to attach cloud and local files to Rails applications; Action Text, a library to handle rich text content; and Active Support, a collection of utility classes and standard library extensions that are useful for Rails, and may also be used independently outside Rails.
Getting Started
-
Install Rails at the command prompt if you haven't yet:
$ gem install rails
-
At the command prompt, create a new Rails application:
$ rails new myapp
where "myapp" is the application name.
-
Change directory to
myapp
and start the web server:$ cd myapp $ rails server
Run with
--help
or-h
for options. -
Go to
http://localhost:3000
and you'll see: "Yay! You’re on Rails!" -
Follow the guidelines to start developing your application. You may find the following resources handy:
Contributing
We encourage you to contribute to Ruby on Rails! Please check out the Contributing to Ruby on Rails guide for guidelines about how to proceed. Join us!
Trying to report a possible security vulnerability in Rails? Please check out our security policy for guidelines about how to proceed.
Everyone interacting in Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Rails code of conduct.
Code Status
License
Ruby on Rails is released under the MIT License.