Some inputs will behave differently depending on what input we choose. Let’s look at the case for
a field named product, we can fetch a Product by either its id or its name. Currently we’d
make a tradeoff for this by introducing two arguments that are both nullable, now if both are passed
as null we’d have to handle that in code. To fix this the @oneOf directive was introduced so we
can create these input-unions without sacrificing the strictly typed nature of our GraphQL Schema.
const schema = buildSchema(`
type Product {
id: ID!
name: String!
}
input ProductInput @oneOf {
id: ID
name: String
}
type Query {
product(input: ProductInput!): Product
}
`);It doesn’t matter whether you have 2 or more inputs here, all that matters is that your user will have to specify one, and only one, for this input to be valid.