Polymorphic chargeable association on Pay::Charge

[mguidetti]

In my application I have two models that can be related to one-off charges, Invoice and FormResponse. Currently, I associate these other records by adding has_one relationships to Pay::Charge with an extension:

included do
  has_one :invoice
  has_one :form_response
end

with an accompanying belongs_to on the Invoice and FormResponse models.

This works, but what would you think about adding a polymorphic "Chargable" association on Pay::Charge? This would allow a built-in way to associate a Pay::Charge record to any other record in an application.

I'd imagine usage being something like:

@user.payment_processor.charge(15_00, chargeable: SomeChargeableRecordInstance)

If this seems like a good idea, I'd be happy to start PR.

[excid3]

There's definitely something that could be good here, although I don't think adding it to the Pay::Charge makes sense since it limits to a single association.

ActiveStorage is a good example of how it should ideally work for maximum use cases:

Blob - the actual uploaded file

• has_many :attachments

Attachment

• belongs_to :blob
• belongs_to :record, polymorphic: true, touch: true

You could apply this approach to both Pay::Subscriptions and Pay::Charges too. Maybe that's a model that should be added to Pay, I'm not sure. Pay::Attachment?

[mguidetti]

Right that's a good idea to allow multiple associations. I'll start that way and see what I can come up with. 👍