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:
A user sends a request to the web server
The web server gets the request and passes it to the controller
The request is then directed to its specific route, like /grocery. The route connects with the controller method that handles this request
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
Once the data is validated, it’s prepared to be shown in the view
The data is sent to the view for display, usually in an HTML file like index.html or index.html.erb
The view processes the data and creates a response to send back to the webserver
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:
Figuring out what to do when a user makes a request
Getting data from the Model and sending it to the View to show to the user
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:
Sitepoint’s MVC Architecture in Rails
Ruby on Rails Official Documentation
Thank you for reading!
