Rails Internals

Image transformations let you show images in the size or format you need. You can create a new version by calling variant on an attachment and passing the desired transformations. When a browser requests that URL, Rails will process the original image on demand and redirect to the generated file.

The new bearer_token method on the Request object is a nice addition to Rails. It removes boilerplate code and simplifies bearer token extraction. All Rails apps can now access bearer tokens the same way without having to write custom token extraction logic every time and worrying about edge cases.

In this post, we'll explore the internals of has_one_attached method in Active Storage. It covers two interesting patterns, i.e. proxy and change objects. We'll trace the control flow from the model DSL to persistence and uploads, and explain how files are created, detached, and purged.

Active Storage uses two main models: blobs and attachments. Blobs store the uploaded file's metadata and a link to the actual file, while attachments link those files to records. Understanding how they work together makes it easier to manage uploads, generate URLs, and process uploaded files.

This post shows how to inspect the sequence of before, after, and around callbacks in Rails controllers by adding a small initializer. Useful for understanding callback order in applications with complex controller hierarchies or shared concerns. I learned this trick while reading the Rails tests.

In this post, we’ll explore how redirects work in Rails: what they are, how to redirect manually, and how the redirect_to method simplifies things. We’ll cover common use cases, security considerations, and even dig into the Rails source to see how redirect_to works under the hood.

The Instrumentation API in ActiveSupport serves a dual purpose. You can use it to implement the observer (pub-sub) pattern, as well as benchmark how long it took to execute some action. In this post, we'll learn almost everything you need to know about the Rails Instrumentation API.

In this post, we will explore how a simple Ruby method, when added to a controller, becomes an action in Rails, ready to process incoming HTTP requests and send responses. We'll also trace the path of an incoming HTTP request to a Rails controller action.

At first glance, Rails initializers seem complex, but they're solving a simple, but important problem: run some code after framework and gems are loaded, to initialize the application. This post covers the basics of initializers, including what they are, how they work, and how Rails implements them.

This article shows how you can access your application models and other constants inside rake tasks by adding the `environment` task as a dependency. We'll also go one level deeper and learn exactly how this task loads the environment by inspecting the Rails source code.

Here're two techniques I've found really helpful for reading the Rails codebase, without getting overwhelmed. If you want to dive into the Rails source code for a deeper understanding, but feel intimidated by the sheer size of the codebase and don't know where to begin, this post is for you.

This is the first post in the Campfire deep dive series where we explore the first ONCE product from 37signals to learn and extract useful patterns, ideas, and best practices. This post explores the direct method in the Rails Router that lets you define custom URL helpers for your application.

This article explains why you shouldn't log confidential or user-identifiable information and how to filter it using parameter filtering in Rails. We'll also do a deep dive into the Rails source code to learn exactly how Rails implements parameter filters.

This post covers the basics of environments in Rails, including what they are, how they work and why they're so important. We'll also take a look behind the scenes and dive into the Rails source code to learn exactly how they're implemented, exploring a few interesting "inquiry" classes in Rails.

Do you want to understand how Active Job works behind the scenes? Reading and understanding the source code is one of the best ways to learn a framework (or anything). This post breaks it all down for you by tracing the journey of a Rails background job, from its creation to execution.

The respond_to method allows the controller to select the appropriate response format based on the request's Accept header or the request URL. You can also use it to handle variants for different screens. This post covers the basics of this method: what it is, how it works and why it's important.

You can enable caching in development mode by running the `rails dev:cache` command in terminal. Ever wondered what that command does, and how exactly does it tell Rails to start caching stuff in your application? Let's take a peek behind the curtain to see exactly what's going on.

Sometimes, you receive a Hash key as a method parameter or via user input, and you want to make the Hash understand that key as-is, without worrying if the key is a string or a symbol. ActiveSupport's `HashWithIndifferentAccess` class lets you accomplish this in a convenient way.

Do you want to read the Rails source code for a deeper understanding of the framework, but feel intimidated by the sheer size of the codebase, or don't know where to start? Start with a specific feature, insert a breakpoint, and step through the method line-by-line. This article shows how.

Autoloading allows you to speed up the initialization of your library by lazily loading the code only when you need it. This post explains how the autoload method works in Ruby and how Rails overrides this method to provide its own implementation that follows the Rails naming conventions.

You must have used the `has_secure_password` macro in Rails. Did you know Rails also provides a `has_secure_token` macro to generate unique tokens on your models? In this article, we'll learn how it works and we'll also see how Rails implements it behind the scenes.

Concerns are an important concept in Rails that can be confusing to understand for those new to Rails as well as seasoned practitioners. This post explains what concerns are, how they work, and how & when you should use them to simplify your code, with practical, real-world examples.

Have you ever wanted to create a hash where you could access the values like methods on an object? The OrderedOptions class in Rails lets you do just that. This post shows you how. We'll also explore how Rails implements this feature using Ruby's metaprogramming features.

In this article, we'll learn how to mark certain attributes as readonly on your active record models, to prevent them from any future updates after the record is created and saved to the database. We'll also learn how Rails implements this feature behind the scenes.

In this post, we will explore the `AttributeAssignment` module in Rails, which allows you to set an object's attributes by passing in a hash, a feature commonly used by Active Record models. We'll also learn a little metaprogramming along the way.

Rails protects your web application from CSRF attack by including an authenticity token in the HTML forms. This token is also stored in the user's session. Upon receiving a request, Rails compares these two tokens to decide if the request is verified.

This article explains the Rails rendering process in the context of returning JSON data from the controller. Hopefully, it will make it clear what really happens when you call the render method from the controller.

In this article, I explain the journey of a background job, from its creation to execution. We will learn how it’s configured and enqueued, and how an adapter invokes it. We will also see the different ways to configure a job.