Payment integration can be challenging when building web applications. The Pay gem makes handling subscriptions and payments a whole lot easier in Rails applications. It integrates applications with Stripe, Paddle, Braintree, or Lemon Squeezy to manage payments. In this article, we will go through one and, in practice, explain how it works and then set it up using a simple example.

What is Pay?

The Pay gem is a library for handling payments and subscriptions in Rails. It abstracts many common tasks, such as:

• Creating and managing customer records on Stripe.
• Handling subscriptions, invoices, and payment methods.
• Managing webhooks for real-time payment updates.

Instead of writing custom code to interact with the Stripe API, Pay provides a Rails-friendly interface that saves time and reduces complexity.

How Does Pay Work?

Pay integrates with your Rails models to handle payments and subscriptions. For example, you can add a pay_customer relationship to your User model, allowing each user to manage their payments. Pay also listens for webhooks from Stripe, so your app stays updated when payments are made or subscriptions change.

Setting Up Pay for Stripe

Here’s how to get started:

1. Install the Gem

Add Pay to your Gemfile and install it:

gem 'pay'

Run the bundle install command to install it:

bundle install

2. Configure Pay

Run the generator to set up Pay’s migrations and configuration:

rails generate pay:install  
rails db:migrate  

Edit the generated config/initializers/pay.rb file to enable Stripe:

Pay.setup do |config|
  config.adapters = [:stripe] # Add Stripe as the payment adapter
  config.default_product_name = "My Awesome App"
  config.default_plan_name = "default-plan"
end

Set your Stripe keys in your environment variables or credentials.yml.enc:

stripe:
  public_key: pk_live_12345
  secret_key: sk_live_12345
  webhook_secret: whsec_12345

3. Connect Pay to Your Models

In your User model, add the Pay::Billable module with using pay_customer method:

class User < ApplicationRecord
  pay_customer
end

This allows users to have payment methods, subscriptions, and invoices.

4. Set Up Stripe Webhooks

To handle real-time updates from Stripe, set up a webhook endpoint. Run this command:

rails generate pay:webhooks

This creates a Pay::Webhooks::StripeController that processes Stripe events. Register the webhook URL in the Stripe dashboard, typically at:

https://your-app.com/pay/webhooks/stripe

Example: Creating a Subscription

Here’s a simple example of how to create a subscription:

1. Add a Button for Payment

In your view, include a form to collect a payment method:

<%= form_with url: stripe_payment_method_path, method: :post do %>
  <div id="card-element"></div>
  <button type="submit">Submit Payment</button>
<% end %>

Stripe provides JavaScript tools to handle card input fields securely.

2. Attach a Payment Method to the User

In the controller:

class StripeController < ApplicationController
  def create_payment_method
    current_user.payment_processor = :stripe
    current_user.payment_processor.save_payment_method(params[:payment_method_id])
    redirect_to subscriptions_path, notice: "Payment method saved!"
  end
end

3. Create a Subscription

Now, you can create a subscription for the user:

class SubscriptionsController < ApplicationController
  def create
    current_user.payment_processor.subscribe(plan: "default-plan")
    redirect_to dashboard_path, notice: "Subscription created!"
  end
end

How Pay Keeps Things Simple

Instead of directly interacting with the Stripe API, Pay handles the heavy lifting. It:

• Saves payment methods and creates customers on Stripe automatically.
• Manages recurring billing through its subscription methods.
• Ensures webhooks update your app without custom code.

Conclusion

The Pay gem simplifies integrating Stripe with Rails. By abstracting common payment tasks, it lets you focus on your app's features instead of payment processing details.

If you’re starting with payments in Rails, consider using Pay—it’s designed to save you time and make your code cleaner.