How to handle Union or Interface in graphQL mutations? - graphql

Question

I got the following schema :
type Vehicle {
id: ID!
name: String!
color: String!
}
input AddVehicle {
name: String!
color: String!
}
input UpdateVehicle {
id: ID!
name: String!
}
Now I would like to add some properties to my vehicles, depending of the Vehicle model, like
type CarProperties {
wheelSize: Int!
doors: Int!
}
type BoatProperties {
length: Int!
}
union VehicleProperties = CarProperties | BoatProperties
type Vehicle {
[ ... ]
properties: vehicleProperties!
}
So it's quite straightforward to write the queries, but I'm struggling when it comes to make mutations...
AFAIK graphQL inputs does not implement unions or interface (There is a related thread here https://github.com/graphql/graphql-spec/issues/488)
So the workaround I see here is to duplicate my inputs, like :
input addBoatVehicle {
name: String!
color: String!
properties: BoatProperties!
}
and so on with updateBoatVehicle, addCarVehicle, updateCarVehicle.
But if I get a lot of vehicle models, or maybe a third or a fourth mutation, I'm afraid it becomes cumbersome quickly.
Is there any recommended way to manage this case ?

Answer 1

Creating separate mutations is the proper solution. You can alleviate some of the pain by making your mutations incredibly lightweight and refactor out processing of those items to a separate function.
function addVehicle(input) {
// disambiguate the input type
}
function updateVehicle(input) {
// dismabiguate the input type, preferably in its own refactor function so
// it can be used above too!
}
const resolvers = {
Mutation: {
addBoat: (parent, boatInput) => { return addVehicle(boatInput) },
addCar: (parent, carInput) => { return addVehicle(carInput) },
updateBoat: (parent, boatInput) => { return updateVehicle(boatInput) },
updateCar: (parent, carInput) => { return updateVehicle(carInput) },
}
}