Pass Graphql input arguement to directive - graphql

Question

I have a simple graphql query and a directive
directive #isOwner(postID: String!) on FIELD_DEFINITION
type Query {
post(postID: String!): Post! #isOwner(postID: postID)
}
The problem is that I'm using GQLGen to generate my boilerplate code for Go, and directives are treated differently from the input values.
This presents a unique challenge where authorization logic is almost isolated from the actual db reads, which makes the logic very inefficient, in that I have to eiither make a database read twice: during validation and the actual db read.
The data required for validation is also required for the db read, and I would have to edit my whole code to inject this data into context.
Is there a way of passing the input arguements dynamically to the directive and have the validation done dynamically and is it a good pracise in the first place?

Answer 1

Arguments passed to schema directives are evaluated when your schema is initially built, so they can't be dynamic. In this particular case, you don't need an argument at all -- you can just read the value of the field's arguments.
visitFieldDefinition(field) {
const { resolve = defaultFieldResolver } = field
field.resolve = async function (parent, args, context, info) {
console.log(args.postID)
return resolve.apply(this, [parent, args, context, info])
}
}
However, if the name of the argument varies by field, then you can pass that as an argument to your directive
directive #isOwner(argName: String!) on FIELD_DEFINITION
visitFieldDefinition(field) {
const { resolve = defaultFieldResolver } = field
const { argName } = this.args
field.resolve = async function (parent, args, context, info) {
console.log(args[argName])
return resolve.apply(this, [parent, args, context, info])
}
}