# Topics

Rails offers several conventions and tools to organize and structure a codebase.  Typically, they help to modularize and DRY up an application. Here are some popular ones:

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### **1. Code Organization and Modularity**

* **Concerns** [***(see ours for Controller files)***](https://aaron-mota.gitbook.io/aarons-style-guide/backend/rails/broken-reference)
  * **Purpose**: To organize and reuse code across models or controllers.
  * **Example**: Using `ActiveSupport::Concern` to extract shared logic from multiple models and put it into a module.
  * **Code Examples**: `included do; before_action :authenticate_user!; end`
* **Helpers**
  * **Purpose**: Assist views by providing reusable methods to handle presentation logic.
  * **Example**: A `date_format` helper that takes a date and returns it in a specific string format.
  * **Code Examples**: `def formatted_date(date); date.strftime('%B %d, %Y'); end`
* **Service Objects**
  * **Purpose**: Encapsulate business logic or actions into plain old Ruby objects, keeping controllers and models slim.
  * **Example**: A `UserRegistrationService` that handles the complexities of registering a user.

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### **2. Data Management**

* **Active Record**
  * **Purpose**: ORM framework to represent and manipulate data in relational databases. Provides a way to create, read, update, and delete records without writing SQL statements.
  * **Example**: `User.find_by(email: 'example@email.com')` to fetch a user by their email address without writing a direct SQL query.
  * **Code Examples**: `User.find_by(email: 'example@email.com')`
* **Scopes**
  * **Purpose**: Provide a way to define commonly-used ActiveRecord queries which can be referenced as method calls on the associated models.
  * **Example**: `published` scope on an `Article` model to fetch only published articles.
  * **Code Examples:** `scope :published, -> { where(published: true) }`
* **Callbacks**
  * **Purpose**: Hook into the lifecycle of an Active Record object to execute logic at certain points.
  * **Example**: Sending a welcome email after a `User` is created.
  * **Code Examples:** `before_save :normalize_name`, `after_create :send_welcome_email`
* **Validators**
  * **Purpose**: Ensure data integrity by checking the validity of model attributes before saving to the database.
  * **Example**: Ensuring a `User` email is present and formatted correctly.
  * **Code Examples**: `validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }`
* **Polymorphic Associations (has\_many, belongs\_to, etc.)**
  * **Purpose**: Allow a model to belong to multiple other types of models on a single association.
  * **Example**: A `Comment` model that can belong to either an `Article` or a `Photo`.
  * **Code Examples**: `has_many :posts`<br>

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### **3. User Interface & Presentation**

* **Partials**
  * **Purpose**: DRY up views by extracting pieces of markup into reusable files.
  * **Example**: A `_header.html.erb` partial that's used across multiple views.
  * **Code Examples**: `<%= render 'shared/footer' %>`
* **View Components (or simply Components)**
  * **Purpose**: Encapsulate parts of the view into reusable and testable units.
  * **Example**: A `NavbarComponent` that renders the navigation bar.

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### **4. Jobs & Background Processing**

* **Active Job**
  * **Purpose**: Framework for declaring background jobs and making them run on various queuing backends.
  * **Example**: Sending bulk emails to users.

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### **5. Mail & Communication**

* **Action Mailer**
  * **Purpose**: Framework for designing email services using templates.
  * **Example**: A `UserMailer` to send welcome emails and password resets.

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### **6. Application Enhancements**

* **Active Storage**
  * **Purpose**: Attach files to ActiveRecord objects.
  * **Example**: Attaching an image to an `Article` object.
  * **Code Examples**: `has_one_attached :profile_picture`
* **Action Text**
  * **Purpose**: Rich text content and editing, integrating with Active Storage for attachments.
  * **Example**: Adding a rich text editor to a blog platform for article creation.
* **Active Job**
  * **Purpose**: Framework for declaring background jobs and making them run on a variety of queueing backends.
  * **Example**: Sending bulk emails in the background.
  * **Code Examples**: `class BulkEmailJob < ApplicationJob; queue_as :default; def perform(*args); # sending email logic here; end; end`

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### **7. Advanced Relations & Associations**

* **Single Table Inheritance (STI)**
  * **Purpose**: Inherit from a base model class, allowing multiple subclasses to have specific behaviors but are stored in a single database table.
  * **Example**: A `Vehicle` model with subclasses `Car` and `Truck`.

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### 8. Routing & Controllers

* **Routes**
  * **Purpose**: Define URLs for your application and how they map to controllers, actions, and views.
  * **Example**: Routing a GET request to `/users` to the `index` action of the `UsersController`.
  * **Code Examples**: `get 'users', to: 'users#index'`
* **Controller Filters (before\_action, after\_action, around\_action)**
  * **Purpose**: Execute methods in a controller before, after, or around the entire action.
  * **Example**: Authenticating a user before granting them access to an action.
  * **Code Examples**: `before_action :authenticate_user!, only: [:edit, :update]`<br>

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Each of these tools and conventions helps Rails developers structure their applications in a maintainable and organized way.