The first thing you'll need to do is add a payment method. You will get a payment method token from the payment processor's Javascript library. See the payment processors docs for how to setup their Javascript.

With Pay, you can simply assign the payment method token before making a charge or subscription.

Pay will attempt to save an API request by creating a Customer and assigning PaymentMethod in the same request if a payment_method_token is set.

@user.payment_processor.payment_method_token = params[:payment_method_token]
@user.payment_processor.charge(15_00)

The payment method will be set as the default, so future payments do not need to collect a payment method.

If a customer would like to purchase and provide a new payment method, you may still assign a payment_method_token before purchasing.

To update the default payment method on file, you can use update_payment_method:

@user.payment_processor.update_payment_method(params[:payment_method_token])

This will add the payment method via the API and mark it as the default for future payments.

Paddle uses an Update Payment Details URL for each customer which allows them to update the payment method. This is stored on the Pay::Subscription record for easy access.

@user.payment_processor.subscription.paddle_update_url

You may either redirect to this URL or use Paddle's Javascript to render as an overlay or inline.

You can also add a payment method without making it the default.

@user.payment_processor.add_payment_method(params[:payment_method_token], default: false)

See Charges