- Rails G Model Foreign Key
- Rails Generate Model References
- Rails Generate Model Foreign Key References List
- Rails Generate Model
- Rails Generate Model Foreign Key
Advanced Rails model generators rails. There are some people who give advice to not use rails generators and create models, controllers and etc. Things manually. I don’t agree with them and my advice here is to figure out deeply how they work and then make conclusion.
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- TableDefinition#references will add an appropriately-named id column, plus a corresponding type column if the:polymorphic option is supplied. If:polymorphic is a hash of options, these will be used when creating the type column. The:index option will also create an index, similar to calling addindex. So what can be written like this.
- Foreign key does not work as expected I know its not 'The Rails Way' but I'm trying to add foreign keys to enforce referential integrity at the db level. I want to create a new table called recipeingredients which will have foreign keys referencing a table called recipes and o.
There are many ways to add the foreign key column that's required by our has_many and belongs_to associations, and I want to take a moment to show you a couple more of them.
There are many ways to add the foreign key column that's required by our
has_many
and belongs_to
associations, and I want to take a moment to show you a couple more of them.- If you want, you can use the
references
column type in migrations instead.bin/rails generate migration AddPostToComments post:references
- That will create a migration with a call to the
add_reference
method instead ofadd_column
.add_reference
takes a symbol with a table name, and a symbol with the name of a model to add a foreign key for. It'll create a column whose name begins with that model name, and ends in_id
. And since it's always desirable to have an index on foreign key columns,add_reference
will add an index as well. Soadd_reference :comments, :post
will create apost_id
column in thecomments
table just likeadd_column
did, but it will also add an index on that column automatically. - The
foreign_key: true
argument will set up a foreign key constraint on databases that support it.
Without a foreign key constraint, we could create a comment with a
post_id
field set to 999
, even if there was no record in the post
table with an id
of 999
. With a foreign key constraint, the database would prevent such a record from even being saved. Foreign key constraints help keep bad data from sneaking into your database.Note that the adapter for the SQLite database that Rails uses by default doesn't support foreign key constraints. Your migration will still work, and it's a good idea to get in the habit of adding the constraints in your migrations. But if you want the database to actually enforce the constraints, you'll need to switch to another database like MySQL or PostgreSQL.
If we know we're going to need an association when we're first creating a model, we can set the necessary columns up then, too.
- Let's re-generate the
Comment
model. We can replace the two migrations with a single migration that creates thecomments
table and adds apost_id
column along with the other columns:rails g model Comment content:text name:string post:references
.- We can allow it to overwrite the existing model class file, as well as another file related to tests.
- Don't forget to run
bin/rails db:migrate
. - We should now be able to create comments associated with a post again.
- 0:00There are many ways to add the foreign_keycolumn that's required by our has_many and
- 0:04belongs_to associations.
- 0:06And I wanna take a moment toshow you a couple more of them.
- 0:09Let's undo our changes to the databaseby rolling back the latest migration.
- 0:13We'll run bin/rails.
- 0:16And we'll run the db:rollback task.
- 0:20That'll go through the commands in thelatest migration and undo them one by one.
- 0:25Then let's get rid ofthe migration we created.
- 0:27We're gonna do thatwith bin/rails destroy,
- 0:31which you can consider to bethe opposite of the generate command.
- 0:35We're gonna destroy the migrationnamed AddPostToComments.
- 0:44That's the latest migration we created.
- 0:47That'll go through,
- 0:48find all the files that were createdby the generator, and delete them.
- 0:52Now let's redo our previous migrationusing the references column type instead.
- 0:56So we're gonna run bin/rails generate.
- 1:02We're gonna generate a migration.
- 1:04And again,it'll be named AddPostToComments.
- 1:09This time, instead of a type of integer,we're going to give it
- 1:14a column name of post anda type of references.
- 1:21That'll create a new migration file.
- 1:27And the file will have a call tothe add_reference method instead of
- 1:31add_column.
- 1:32add_reference takes a symbol with a tablename and a symbol with the name of
- 1:36a model to add a foreign_key for,in this case, the post model.
- 1:41It'll create a column whose namebegins with that model name and
- 1:45ends in underscore ID.
- 1:47And since it's always desirable tohave an index on foreign_key columns,
- 1:50add_reference will add an index as well.
- 1:53So add_reference :comments,
- 1:54:post will create a post_id column in thecomments table, just like add_column did.
- 1:59But it'll also add an indexon that column automatically.
- 2:03The foreign_key: true argument willset up a foreign_key constraint
- 2:07on databases that support it.
- 2:10Without a foreign_key constraint, we couldcreate a comment with a post_id field set
- 2:14to 999, even if there was no recordin the post table with an ID of 999.
- 2:21But with a foreign_key constraint,
- 2:23the database would prevent sucha record from even being saved.
- 2:27Note that the adapter for the SQL-likedatabase that Rails uses by default
- 2:31doesn't support foreign_key constraints.
- 2:34Your migration will still work.
- 2:35And it's a good idea to get in the habitof adding the constraints in your
- 2:38migrations.
- 2:40But if you want the database toactually enforce the constraints,
- 2:43you'll need to switch to anotherdatabase like MySQL or PostgreSQL.
- 2:47See the teacher's notes if you'dlike more info on doing so.
- 2:51Now that we have our new migration,let's try running it.
- 2:54bin/rails db:migrate.
- 3:01It'll add a post_id field backto our comments table again.
- 3:04And if we launch a Rails console, we'll beable to add comments to our post again.
- 3:11So if we were to take the first post and
- 3:16create a comment on itwith comments.create,
- 3:21we'll give it content of HI.
- 3:27And the commenter name is gonna be Jay.
- 3:31And if we pretty print the listof the first post comments,
- 3:37we can see the comment's been added.
- 3:42If we know we're going to needan association when we're first
- 3:45creating a model, we can setthe necessary columns up then, too.
- 3:49Let's start by getting our databaseback to the point it was at
- 3:52before we created the comments model.
- 3:54Since we've only set up the commentstable on our development machine,
- 3:57we can just undo the migrationsthat created it.
- 4:00We can list out the migrations in ourdb/migrate directory with ls db/migrate.
- 4:08You might need to use a slightly differentcommand to list the directory contents if
- 4:12you're on Windows.
- 4:13We can see that the two most recentmigrations are add_post_to_comments and
- 4:18create_comments.
- 4:20Let's roll back our migration that addsthe post_id field to the comments table.
- 4:24bin/rails db:rollback.
- 4:30Then let's roll back the migrationthat created the comments table.
- 4:33bin/rails db:rollback again.
- 4:36Now let's get rid of thoselast two migrations.
- 4:39bin/rails destroy,
- 4:44The migration named AddPostToComments.
- 4:52And then we'll also destroythe migration named CreateComments.
- 5:00Now let's regenerate the comment model.
- 5:02We can replace the two migrations with asingle migration that creates the comments
- 5:07table and adds a post_id columnalong with the other columns.
- 5:10So we'll say bin/rails
- 5:14generate model Comment.
- 5:19We'll set up a contentattribute of type text and
- 5:24commenter name attribute of type string.
- 5:28And post:references willset up the post_id field.
- 5:35If it asks to overwrite any existingfiles, it should be okay to allow it.
- 5:39We generated the migration, sodon't forget to run bin/rails db:migrate.
- 5:47And if we launch bin/rails console,
- 5:52we should be able to create commentsassociated with post again.
- 5:55So let's say post = Post.first,
- 6:01post.comments.create.
- 6:05And we'll give it content of Hi anda commenter name of Alena.
- 6:15And if we run Post.first.comments,it should bring up our new comment.
- 6:22Now you know several ways tosetup a has_many association.
- 6:26In the next few videos, we're goingto take a look at some of the other
- 6:28associations that Active Record supports
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This tutorial assumes you have basic Rails knowledge from reading the Getting Started with Rails Guide.
1 Command Line Basics
There are a few commands that are absolutely critical to your everyday usage of Rails. In the order of how much you'll probably use them are:
rails console
rails server
rails test
rails generate
rails db:migrate
rails db:create
rails routes
rails dbconsole
rails new app_name
You can get a list of rails commands available to you, which will often depend on your current directory, by typing
rails --help
. Each command has a description, and should help you find the thing you need.![Rails Generate Model Foreign Key References Rails Generate Model Foreign Key References](/uploads/1/2/6/0/126076584/159465405.png)
Let's create a simple Rails application to step through each of these commands in context.
1.1 rails new
The first thing we'll want to do is create a new Rails application by running the
rails new
command after installing Rails.You can install the rails gem by typing
gem install rails
, if you don't have it already.Rails will set you up with what seems like a huge amount of stuff for such a tiny command! You've got the entire Rails directory structure now with all the code you need to run our simple application right out of the box.
1.2 rails server
The
rails server
command launches a web server named Puma which comes bundled with Rails. You'll use this any time you want to access your application through a web browser.With no further work,
rails server
will run our new shiny Rails app:With just three commands we whipped up a Rails server listening on port 3000. Go to your browser and open http://localhost:3000, you will see a basic Rails app running.
You can also use the alias 's' to start the server:
rails s
.The server can be run on a different port using the
-p
option. The default development environment can be changed using -e
.The
-b
option binds Rails to the specified IP, by default it is localhost. You can run a server as a daemon by passing a -d
option.1.3 rails generate
The
rails generate
command uses templates to create a whole lot of things. Running rails generate
by itself gives a list of available generators:You can also use the alias 'g' to invoke the generator command:
rails g
.You can install more generators through generator gems, portions of plugins you'll undoubtedly install, and you can even create your own!
Using generators will save you a large amount of time by writing boilerplate code, code that is necessary for the app to work.
Let's make our own controller with the controller generator. But what command should we use? Let's ask the generator:
All Rails console utilities have help text. As with most *nix utilities, you can try adding
--help
or -h
to the end, for example rails server --help
.The controller generator is expecting parameters in the form of
generate controller ControllerName action1 action2
. Let's make a Greetings
controller with an action of hello, which will say something nice to us.What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file, and a stylesheet file.
Check out the controller and modify it a little (in
app/controllers/greetings_controller.rb
):Then the view, to display our message (in
app/views/greetings/hello.html.erb
):Fire up your server using
rails server
.The URL will be http://localhost:3000/greetings/hello.
With a normal, plain-old Rails application, your URLs will generally follow the pattern of http://(host)/(controller)/(action), and a URL like http://(host)/(controller) will hit the index action of that controller.
Rails comes with a generator for data models too.
For a list of available field types for the
type
parameter, refer to the API documentation for the add_column method for the SchemaStatements
module. The index
parameter generates a corresponding index for the column.But instead of generating a model directly (which we'll be doing later), let's set up a scaffold. A scaffold in Rails is a full set of model, database migration for that model, controller to manipulate it, views to view and manipulate the data, and a test suite for each of the above.
We will set up a simple resource called 'HighScore' that will keep track of our highest score on video games we play.
The generator checks that there exist the directories for models, controllers, helpers, layouts, functional and unit tests, stylesheets, creates the views, controller, model and database migration for HighScore (creating the
high_scores
table and fields), takes care of the route for the resource, and new tests for everything.The migration requires that we migrate, that is, run some Ruby code (living in that
20130717151933_create_high_scores.rb
) to modify the schema of our database. Which database? The SQLite3 database that Rails will create for you when we run the rails db:migrate
command. We'll talk more about that command below.Let's talk about unit tests. Unit tests are code that tests and makes assertionsabout code. In unit testing, we take a little part of code, say a method of a model,and test its inputs and outputs. Unit tests are your friend. The sooner you makepeace with the fact that your quality of life will drastically increase when you unittest your code, the better. Seriously. Please visitthe testing guide for an in-depthlook at unit testing.
Windows xp sp3 professional product key generator windows 10. Let's see the interface Rails created for us.
Go to your browser and open http://localhost:3000/high_scores, now we can create new high scores (55,160 on Space Invaders!)
1.4 rails console
The
console
command lets you interact with your Rails application from the command line. On the underside, rails console
uses IRB, so if you've ever used it, you'll be right at home. This is useful for testing out quick ideas with code and changing data server-side without touching the website.You can also use the alias 'c' to invoke the console:
rails c
.You can specify the environment in which the
console
command should operate.If you wish to test out some code without changing any data, you can do that by invoking
rails console --sandbox
.1.4.1 The app and helper objects
Inside the
rails console
you have access to the app
and helper
instances.With the
app
method you can access named route helpers, as well as do requests.With the
helper
method it is possible to access Rails and your application's helpers.1.5 rails dbconsole
rails dbconsole
figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL (including MariaDB), PostgreSQL, and SQLite3.You can also use the alias 'db' to invoke the dbconsole:
rails db
.1.6 rails runner
runner
runs Ruby code in the context of Rails non-interactively. For instance:You can also use the alias 'r' to invoke the runner:
rails r
.You can specify the environment in which the
runner
command should operate using the -e
switch.You can even execute ruby code written in a file with runner.
1.7 rails destroy
Think of
destroy
as the opposite of generate
. It'll figure out what generate did, and undo it.You can also use the alias 'd' to invoke the destroy command:
rails d
.1.8 rails about
rails about
gives information about version numbers for Ruby, RubyGems, Rails, the Rails subcomponents, your application's folder, the current Rails environment name, your app's database adapter, and schema version. It is useful when you need to ask for help, check if a security patch might affect you, or when you need some stats for an existing Rails installation.1.9 rails assets:
You can precompile the assets in
app/assets
using rails assets:precompile
, and remove older compiled assets using rails assets:clean
. The assets:clean
command allows for rolling deploys that may still be linking to an old asset while the new assets are being built.If you want to clear
public/assets
completely, you can use rails assets:clobber
.1.10 rails db:
The most common commands of the
db:
rails namespace are migrate
and create
, and it will pay off to try out all of the migration rails commands (up
, down
, redo
, reset
). rails db:version
is useful when troubleshooting, telling you the current version of the database.More information about migrations can be found in the Migrations guide.
1.11 rails notes
rails notes
searches through your code for comments beginning with a specific keyword. You can refer to rails notes --help
for information about usage.By default, it will search in
app
, config
, db
, lib
, and test
directories for FIXME, OPTIMIZE, and TODO annotations in files with extension .builder
, .rb
, .rake
, .yml
, .yaml
, .ruby
, .css
, .js
, and .erb
.1.11.1 Annotations
You can pass specific annotations by using the
--annotations
argument. By default, it will search for FIXME, OPTIMIZE, and TODO.Note that annotations are case sensitive.1.11.2 Tags
Rails G Model Foreign Key
You can add more default tags to search for by using
config.annotations.register_tags
. It receives a list of tags.1.11.3 Directories
You can add more default directories to search from by using
config.annotations.register_directories
. It receives a list of directory names.1.11.4 Extensions
You can add more default file extensions to search from by using
config.annotations.register_extensions
. It receives a list of extensions with its corresponding regex to match it up.1.12 rails routes
rails routes
will list all of your defined routes, which is useful for tracking down routing problems in your app, or giving you a good overview of the URLs in an app you're trying to get familiar with.1.13 rails test
A good description of unit testing in Rails is given in A Guide to Testing Rails Applications
Rails comes with a test framework called minitest. Rails owes its stability to the use of tests. The commands available in the
test:
namespace helps in running the different tests you will hopefully write.1.14 rails tmp:
The
Rails.root/tmp
directory is, like the *nix /tmp directory, the holding place for temporary files like process id files and cached actions.The
tmp:
namespaced commands will help you clear and create the Rails.root/tmp
directory:rails tmp:cache:clear
clearstmp/cache
.rails tmp:sockets:clear
clearstmp/sockets
.rails tmp:screenshots:clear
clearstmp/screenshots
.rails tmp:clear
clears all cache, sockets, and screenshot files.rails tmp:create
creates tmp directories for cache, sockets, and pids.
1.15 Miscellaneous
rails stats
is great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio.rails secret
will give you a pseudo-random key to use for your session secret.rails time:zones:all
lists all the timezones Rails knows about.
1.16 Custom Rake Tasks
Custom rake tasks have a
.rake
extension and are placed inRails.root/lib/tasks
. You can create these custom rake tasks with therails generate task
command.To pass arguments to your custom rake task:
You can group tasks by placing them in namespaces:
Invocation of the tasks will look like:
If you need to interact with your application models, perform database queries, and so on, your task should depend on the
environment
task, which will load your application code.2 The Rails Advanced Command Line
More advanced use of the command line is focused around finding useful (even surprising at times) options in the utilities, and fitting those to your needs and specific work flow. Listed here are some tricks up Rails' sleeve.
2.1 Rails with Databases and SCM
When creating a new Rails application, you have the option to specify what kind of database and what kind of source code management system your application is going to use. This will save you a few minutes, and certainly many keystrokes.
Let's see what a
--git
option and a --database=postgresql
option will do for us:We had to create the gitapp directory and initialize an empty git repository before Rails would add files it created to our repository. Let's see what it put in our database configuration:
Rails Generate Model References
It also generated some lines in our
database.yml
configuration corresponding to our choice of PostgreSQL for database.Studio one 3 product key generator. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the
rails new
command to generate the basis of your app.Feedback
You're encouraged to help improve the quality of this guide.
Please contribute if you see any typos or factual errors. To get started, you can read our documentation contributions section.
Rails Generate Model Foreign Key References List
You may also find incomplete content or stuff that is not up to date. Please do add any missing documentation for master. Make sure to check Edge Guides first to verify if the issues are already fixed or not on the master branch. Check the Ruby on Rails Guides Guidelines for style and conventions.
Rails Generate Model
If for whatever reason you spot something to fix but cannot patch it yourself, please open an issue.
Rails Generate Model Foreign Key
And last but not least, any kind of discussion regarding Ruby on Rails documentation is very welcome on the rubyonrails-docs mailing list.