Rails Generate Scaffold Foreign Key
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Dec 02, 2014 See the documentation for Foreigner and Rails 4.2. Adding Foreign Key Constraints to an Existing Application With immigrant, you can automatically generate a migration that will add any foreign key constraints your application is missing. With immigrant added to your Gemfile, run rails generate immigration addforeignkeys to create the migration.
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Rails Generate Scaffold Foreign Keys
- Sep 24, 2019 ##Scaffolding in Rails. Rails' scaffolding tool is a quick way to generate some of the major pieces of code in an application. This saves a lot of time when you want to get up-and-running quickly! (It is super cool!) Depending on what you want to create, scaffolding can auto-generate all or a.
- Rails: Generate Model vs. Scaffold July 15, 2014 by Koren Leslie Cohen If you’re just learning Ruby on Rails, you may be confused as to when to generate individual models, resources or scaffolding, and what files are created by each command.
- Adds a new foreign key. Fromtable is the table with the key column, totable contains the referenced primary key. The foreign key will be named after the following pattern: fkrails. Identifier is a 10 character long string which is deterministically generated from the fromtable and column.
While you're developing Rails applications, especially those which are mainly providing you with a simple interface to data in a database, it can often be useful to use the scaffold method.
Scaffolding provides more than cheap demo thrills. Here are some benefits −
You can quickly get code in front of your users for feedback.
You are motivated by faster success.
You can learn how Rails works by looking at the generated code.
You can use scaffolding as a foundation to jump start your development.
Scaffolding Example
To understand scaffolding, let's create a database called cookbook and a table called recipes.
Creating an Empty Rails Web Application
Open a command window and navigate to where you want to create this cookbook web application. So, run the following command to create a complete directory structure.
Setting up the Database
Here is the way to create a database −
To instruct Rails how to find the database, edit the configuration file cookbookconfigdatabase.yml and change the database name to cookbook. Leave the password empty. When you finish, it should look as follows −
Rails lets you run in the development mode, test mode, or production mode, using different databases. This application uses the same database for each.
The Generated Scaffold Code
With the scaffold action, Rails generates all the code it needs dynamically. By running scaffold as a script, we can get all the code written to disk, where we can investigate it and then start tailoring it to our requirements.
So now, let's start once again to generate Scaffold code manually by using the scaffold helper script −
It generates auto-files as shown below −
The Controller
Let's look at the code behind the controller. This code is generated by the scaffold generator. If you open app/controllers/recipes_controller.rb, then you will find something as follows −
When the user of a Rails application selects an action, e.g. 'Show' - the controller will execute any code in the appropriate section - 'def show' - and then by default will render a template of the same name - 'show.html.erb'. This default behavior can be overwritten.
The controller uses ActiveRecord methods such as find, find_all, new, save, update_attributes, and destroy to move data to and from the database tables. Note that you do not have to write any SQL statements, rails will take care of it automatically.
This single line of code will bring the database table to life. It will provide with a simple interface to your data, and ways of −
- Creating new entries
- Editing current entries
- Viewing current entries
- Destroying current entries
When creating or editing an entry, scaffold will do all the hard work like form generation and handling for you, and will even provide clever form generation, supporting the following types of inputs −
- Simple text strings
- Text areas (or large blocks of text)
- Date selectors
- Date-time selectors
You can use Rails Migrations to create and maintain tables.
Now, go to the cookbook directory and run the Web Server using the following command −
Now, open a browser and navigate to http://127.0.0.1:3000/recipe/new. This will provide you a screen to create new entries in the recipes table. A screenshot is shown below −
Once you press the Create button to create a new recipe, your record is added into the recipes table and it shows the following result −
You can see the option to edit, show, and destroy the records. So, play around with these options.
You can also list down all the recipes available in the recipes table using the URL http://127.0.0.1:3000/recipe/list.
Enhancing the Model
Rails gives you a lot of error handling for free. To understand this, add some validation rules to the empty recipe model −
Modify app/models/recipe.rb as follows and then test your application −
These entries will give automatic checking.
validates_length_of − the field is not blank and not too long.
validates_uniqueness_of − duplicate values are trapped. Instead of the default Rails error message, we have given a custom message here.
Alternative Way to Create Scaffolding
Create an application as shown above and The Generated Scaffold Code as shown below
Above code generates the auto files with data base by using with sqlite3 with tittle and instruction column as shown below an image.
we need to migrate the data base by using below syntax.
Finally run the application by using the following command line − Windows 7 home premium sp1 key generator free.
It will generate the result as shown above output images.
The Views
All the views and corresponding all the controller methods are created by scaffold command and they are available in the app/views/recipes directory.
How Scaffolding is Different?
If you have gone through the previous chapters, then you must have seen that we had created methods to list, show, delete and create data etc., but scaffolding does that job automatically.
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.
Rails Generate Scaffold Foreign Key Code
In this post I will describe the most often and useful generator - it’s a model generator. I bet if you don’t use rails generators yet this post will make you to change your work. Using Rails generators saves your time, increases performance, helps to get consistent data for your application.
Basic usage
Let’s start with simple example:
This command will generate user model with email field type of string, migration which creates users table, test for model and factory (if you have it). You are able to generate model with few fields like this:
This example will generate yet model with 3 string fields: first_name, last_name and email.
If you want to have model with different type of string pass type after field name following by : and type. Example:
The whole list of available types:
You are able to pass –option parameter to generator. It will inherit generating class from passed name to achieve STI (sing table inheritance):
This example generates model:
Interesting fact that if you generate model in some scope passing model like admin/user or Admin::User:
you will get generated model in scope app/models/admin/user.rb, defined scope app/models/admin.rb which is requred to define module. Let’s see to the content of generated module:
It means that generated table name for Admin::User starts with prefix admin_users. This feature allows to have separated namespaced models as in rails code as in db schema. Very convenient and useful feature for multimodule applications for my opinion.
Advanced usage
Sometimes you have to automatically add index for columns in your migration. It’s not a problem:
Or uniq index:
Set limit for field of integer, string, text and binary fields:
Special syntax to generate decimal field with scale and precision:
Pay attention that you have to wrap parameter price:decimal{10,2} to quotes. It’s vital and you may have incorrect behavior of generator if you don’t do it. Full explanation of this case is here.
You can combine any single curly brace option with the index options:
And the last useful feature of generators - it’s options to generate reference columns (fields which are used in rails as foreign keys):
This command will generate photos table with integer field album_id and also it will add index for this field automatically. Make sure in it by looking at generated migration:
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For polymorphic reference use this syntax:
Polymorphic reference with indexes:
Conclusion
As you see there a lot of useful things in rails model generator which can decrease your developing time. Thank you for reading this trolling post but anyway I hope you find it useful because I didn’t find any similar post or literature which describes rails model generator fully.
PS. Foundation for this post was got from this rails description usage which is located only in sources of rails on github.