prismaNode implementing an interface

[danielbuechele]

I have a couple of Prisma objects implementing the same interface:

builder.prismaNode('Product', {
  id: {field: 'id'},
  interfaces: [Billable],
})

However, this way I can't have a Product class which extends my Billable class and therefore not use the instanceof check to decide if my object is an instance of Product. I can manually check the existence of certain properties to determine which type my object is, are there any other ways to do this?
One way I can think of is not using prismaNode but instead node from the relay-plugin, but then I'm losing the convenience of the prisma-plugin.
Any other ideas?

[hayes]

This is a complicated problem to solve.

isTypeOf or resolveType are needed only for fields that return an abstract type (interface or union). If you are only using an interface to share fields, then those methods are not required.

In all other cases, there are multiple potential types an object could be. Prisma unfortunately does not provide any identifying information on which table a record is from (there is an open issue requesting this as a feature), but even if it did, Pothos allows multiple graphql object types to be created for the same table. This means we need some hints from the user/app to figure out those types.

We can do this 3 different ways:

An isTypeOf check as you mentioned. This will run whenever this object type is returned, not just when used for an interface or union

A resolveType check on the union or interface, this will only run as needed.

The final option isn't really documented, but the ref returned when creating a prismaObject has an addTypeBrand method on it that can be used to brand an object or list of objects as a specific type in a resolver. The default resolveType method knows how to detect these brands and doesn't require any additional setup. You only need to use thos in resolvers that return an abstract type

[hayes]

Method is actually just addBrand: https://github.com/hayes/pothos/blob/main/packages/plugin-prisma/src/node-ref.ts#L11

[danielbuechele]

Thanks for your help! I do have a follow up question on the same topic. I'm using a class to define my interface, now I have multiple prismaNodes implementing this interface. Ideally I would want to override some of the methods defined on my interface class for each prismaNode. But as I don't manually define the class for each prismaNode, I can't think of a way to do this. Am I missing something?

[danielbuechele]

Thanks, really appreciate your help here. I was able to solve my issue with the type checker. TypeScript now properly flags the issue that my prismaNode is not implementing the getInt function (as shown in your screenshot). So far so good! But I couldn't fully follow your description on how I now would add an implementation for getInt on the prismaNode.
So you are suggesting that instead of using a class and builder.interfaceType(Billable, {...}) I should use an interfaceRef for the definition of the interface? What I am missing is the understanding how I would then define the function for my prismaNode.

[hayes]

basically you can't do that while using the prisma plugin. The prisma plugin is all about defining garphql types based on the data returned by prisma, and prisma doesn't return classes.

You could opt not to use the prisma plugin, or you can change how you define your interface. I'm not sure why you want to use a class for your interface here, but you could do something like this:

[hayes]

you could also detect if root is a user, and then handle that case in the myField resolver.

[hayes]

another potential pattern:

[hayes]

could move the map to the toClass method so you don't have to repeat it on each implementation of MyInterface 🤷