Simplify Authorization in Ruby on Rails With the Power of Pundit Gem

Hi, I'm Denis, a backend developer. I’ve been recently working on building a robust all-in-one CRM system for HR and finance, website, and team management. Using the Pundit gem, I was able to build such an efficient role-based access system, and now I'd like to share my experience.

Managing authorization efficiently became a crucial challenge as this system expanded, requiring a solution that was both scalable and easy to maintain. In Ruby on Rails, handling user access can quickly become complex, but the Pundit gem.

In this article, I will explore how Pundit simplifies authorization, its core concepts, and how you can integrate it seamlessly into your Rails project. By the end of this guide, you'll hopefully have a clear understanding of how to use Pundit effectively to manage user permissions and access control in your Rails applications.

Why Choose Pundit for Authorization?

Pundit is a lightweight and straightforward authorization library for Rails that follows the policy-based authorization pattern. Unlike other authorization libraries, such as CanCanCan, which rely on rule-based permissions, Pundit uses plain Ruby classes to define access rules.

Some key benefits of Pundit include:

• Simplicity: Uses plain old Ruby objects (POROs) to define policies, making it easy to read and maintain.
• Flexibility: Provides fine-grained control over permissions, allowing complex authorization rules to be implemented easily.
• Scalability: Easily extendable as your application grows without adding unnecessary complexity.
• Security: Encourages explicit authorization checks, reducing the risk of unauthorized access to resources.

Unlike role-based systems that define broad roles, Pundit allows for granular, action-specific permission handling. This approach improves maintainability and prevents bloated permission models.

Pundit vs. CanCanCan

Pundit and CanCanCan are both popular authorization libraries for Rails, but they take different approaches:

If you need explicit, granular control over access, Pundit is often the better choice. If you prefer a more declarative, centralized way of defining permissions, CanCanCan might be suitable.

Getting Started With Pundit

Before diving into using Pundit, it’s important to understand how it fits into Rails’ authorization system. By relying on clear, independent policies, Pundit keeps your code maintainable and easy to follow. Now, let’s walk through the setup process and see how you can start using Pundit to manage access control in your application.

1. Installing Pundit Gem

To begin using Pundit in your Rails project, add it to your Gemfile and run bundle install:

Then, install Pundit by running:

This command generates an ApplicationPolicy base class that will be used for defining your policies. This base class provides default behavior for authorization checks and serves as a template for specific policies you create for different models.

2. Defining Policies

Policies in Pundit are responsible for defining authorization rules for a given model or resource. A policy is simply a Ruby class stored inside the app/policies/ directory. For example, let’s generate a policy for a Post model:

This generates a PostPolicy class inside app/policies/post_policy.rb. A basic policy class looks like this:

Each method defines an action (e.g., show?, update?, destroy?) and returns true or false based on whether the user has permission to perform that action. Keeping policy methods small and specific makes them easy to read and debug.

3. Using Policies in Controllers

In your controllers, you can leverage Pundit's authorize method to enforce policies. Here’s how you can integrate Pundit into a PostsController:

Here, authorize @post automatically maps to PostPolicy and calls the appropriate method based on the controller action. This ensures authorization is consistently checked before performing actions on a resource.

4. Handling Authorization at the View Level

Pundit provides the policy helper, which allows you to check permissions in views:

You can also use policy_scope to filter records based on permissions:

This ensures that only authorized data is displayed to the user, preventing unauthorized access even at the UI level (but data loading with policy scope is recommended on the non-view level).

5. Custom Scopes for Querying Data

Pundit allows you to define custom scopes for fetching data based on user roles. Modify PostPolicy to include a Scope class:

In the controller:

This ensures users only see records they are authorized to view, adding an extra layer of security and data privacy. In our experience, it is often necessary to load data from another scope, and then you need to specify additional parameters when loading data from the policy scope:

Also, when you have several scopes for one policy, you can specify which one you need (because by default, the scope uses the "resolve" method for scope). For example, in your policy, you have:

And you can call it:

6. Rescuing a Denied Authorization in Rails

It's important not only to verify authorization correctly but also to handle errors and access permissions properly. In my implementation, I used role-based access rules to ensure secure and flexible control over user permissions, preventing unauthorized actions while maintaining a smooth user experience. I won’t be dwelling a lot upon them in this article, as I described them in detail in one of my recent CRM overviews.

Pundit raises a Pundit::NotAuthorizedError you can rescue_from in your ApplicationController. You can customize the user_not_authorized method in every controller.

So you can also change the behavior of your application when access is denied.

Best Practices for Using Pundit

To get the most out of Pundit, it's essential to follow best practices that ensure your authorization logic remains clean, efficient, and scalable. Let’s explore some key strategies to keep your policies well-structured and your application secure.

1. Сreating a Separate Module: A Clean and Reusable Approach

A well-structured application benefits from modularization, reducing repetitive code, and improving maintainability. Module encapsulates authorization logic, making it easy to reuse across multiple controllers. Let’s break it down: The load_and_authorize_resource method is a powerful helper that:

• Loads the resource based on controller actions.
• Authorizes the resource using Pundit.
• Automatically assigns the loaded resource to an instance variable for use in the controller actions.

Example:

This means that controllers no longer need to explicitly load and authorize records, reducing boilerplate code. For example, the load_and_authorize method dynamically loads records based on controller actions:

• index: Loads all records.
• new/create: Initializes a new record.
• Other actions: Fetches a specific record using a flexible find strategy.

This makes it easy to add authorization without cluttering individual controllers.

2. Applying It in a Controller

With the AuthorizationMethods module included in ApplicationController, controllers become much cleaner. For example, in PostsControllerloading and authorizing a Post record is as simple as:

With load_and_authorize_resource, the controller: 

• ✅ Automatically loads Post records
• ✅ Ensures authorization is enforced 
• ✅ Remains clean and maintainable

Other Best Practices for Pundit

1. Keep policies concise and focused. Each policy should only contain logic related to authorization to maintain clarity and separation of concerns.
2. Use scopes for query-level authorization. This ensures that unauthorized data is never retrieved from the database, improving both security and efficiency.
3. Always call authorize in controllers. This prevents accidental exposure of sensitive actions by ensuring explicit permission checks.
4. Avoid authorization logic in models. Keep concerns separate by handling authorization in policies rather than embedding logic within models.

Wrap Up

Pundit simplifies authorization in Ruby on Rails by providing a clean and structured way to define and enforce permissions. By using policies, scopes, and controller-based authorization, you can create secure, maintainable, and scalable applications with minimal complexity. 

If you’re building a Rails app that requires role-based access control, Pundit is a powerful tool that can streamline your authorization logic while keeping your codebase clean and easy to manage.