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MVC: The Linchpin Architecture of Ruby on Rails

— Dev, Design pattern, Interview preparation, English — 4 min read

When it comes to web development, knowing your architectural patterns is key to building solid and easy-to-maintain apps. And one of the stars in the Ruby on Rails world is MVC—which stands for Model-View-Controller. So, let's cover some key points on what MVC is and how it plays a big role in Rails development.

Explaining MVC in Ruby on Rails

In Rails, you get the MVC model right out of the box, embodying the convention over configuration principle that Rails is known for. It's like having a roadmap that tells you where to go without sweating the small stuff. This setup helps devs concentrate on the fun stuff—like cooking up new features—instead of struggling with naming and organizing files within the project.

Basic Web Request Flow in Rails MVC

For knowledge purposes, understanding how a simple web request moves through the MVC can make things clearer. Here's a simple breakdown of how it works:

  1. A user sends a request to the web server
  2. The web server gets the request and passes it to the controller
  3. The request is then directed to its specific route, like /grocery. The route connects with the controller method that handles this request
  4. The controller talks to the model to get the needed data from the database. It then processes this data based on the app's logic
  5. Once the data is validated, it's prepared to be shown in the view
  6. The data is sent to the view for display, usually in an HTML file like index.html or index.html.erb
  7. The view processes the data and creates a response to send back to the webserver
  8. This response, along with any JSON data, is then sent back to the user's browser

The Model

The Model in MVC is like the brain of the operation. It's where your business logic resides and where all the smarts and data magic happen in your app. In a nutshell, here's what you need to know about the Model:

  • It encapsulates data-related business logic
  • Each Model corresponds to a table in the database
  • While the Model class name is by convention in singular, its equivalent table name in the database is plural
  • It inherits from ActiveRecord::Base which brings some facilities, such as:
    • Establish and maintain a connection with the database
    • Enable data retrieval from the database
    • Facilitate data writing to the database
  • ActiveRecord::Base provides abstractions of database adapters to connect with a wide range of popular databases
  • It also makes it easy to define relationships or associations between models

The View

The View part handles how users interact with the app and how things look on the screen. Here's what you need to know about it:

  • It deals with how things look and how you interact with the browser
  • It's not for handling business stuff or talking to databases
  • It's purpose is only for object representation
  • It mixes HTML and Ruby code using special tags like <%= %> and <% %>
  • The instantiation of this class is done under the hood by the ActionView module
  • The Rails developer only needs to modify the templates that resides on app/views
  • The folder that stores the template file is named after the controller action name. For eg., index.html.erb, or show.html.erb
  • The template has a one-to-one mapping to the controller action
  • The extension of the template can be:
    • html.erb
    • xml.builder
    • json.builder
  • It comes with special templates such as layouts and partials
    • Layouts: are templates that control the global layout of the application and are things that might not change, such as the nav bar
    • Partials: are special subtemplates that can be reused multiple times within the application
  • Communication between controllers and views is made via instance variables
  • All of this is done as part of the ActionPack lib

The Controller

The Controller acts as the intermediary between the Model and the View, handling requests and coordinating data flow. Key aspects of the Controller include:

  • It's the interface that glues the logic that resides in the Model classes and display them into pages that the final user can view. This is done with:
    1. Figuring out what to do when a user makes a request
    2. Getting data from the Model and sending it to the View to show to the user
    3. Gathering info from a browser request and use to create or update a model
  • It's inherits from application_controller.rb that inherits from ActionController::Base
  • Controller class names use CamelCase
  • File names are lowercase with underscores, ending in _controller.rb
  • Each controller handles a specific part of the app
  • Controllers have instance methods that match up with create, read, update, and delete (CRUD) actions

Pros and Cons of MVC in Rails

Pros

  • Scalability: MVC promotes a structured approach that scales well with growing applications
  • Maintainability: Separation of concerns makes code easier to maintain and update
  • Reusability: Components like views and partials can be reused across the application

Cons

  • Complexity: There are some magic things that happen behind the scenes that, at first sight, might be confusing, especially for new developers
  • Partial Knowledge: While MVC is essential, it's part of a larger application architecture, and understanding other design patterns is beneficial

Conclusion

MVC in Ruby on Rails is a common approach used in many projects, and understanding it is crucial if you want to work on Rails projects. This architecture follows certain conventions that help developers focus on important tasks and take advantage of built-in methods and tools provided by the framework. While Rails apps aren't solely based on MVC, from my experience point of view, knowing other design patterns also helps in building software effectively with MVC.

As you can see, this post doesn't cover all the details of this design pattern. The goal here is to provide some guidance and key points to focus on. Hopefully, this gives you a starting point to learn more about the subject, just like it did for me.

For further reading and references, check out the following links:

Thank you for reading!