Resolver Hooks

Intro

---

Sometimes you might need to run function(s), pre or post your resolver. You could use Schema Directives with IdioDirectives. Resolver hooks allow you to achieve similar heights.

Hooks are available on any GraphQLNode or GraphQLType resolver exempt from Subscriptions.

GraphQLNode

GraphQLType

new GraphQLNode({
    name: "User",
    typeDefs: gql`
        type User {
            name: String
        }

        type Query {
            users: User
        }
    `,
    resolvers: {
        Query: {
            users: {
                pre: isRequestAdmin,
                resolve: () => { ... },
                post: updateAudit
            }
        }
    }
})

new GraphQLType({
    name: "Metadata",
    typeDefs: gql`
        type Metadata {
            lastLogin: String
        }
    `,
    resolvers: {
        lastLogin: {
            pre: isRequestAdmin,
            resolve: () => { ... },
            post: updateAudit
        }
    }
})

Multiple hooks

---

An array of functions to be resolved sequentiality.

Query: {
    users: {
        pre: [isRequestAdmin, canRequest(view("users"))],
        resolve: () => { ... }
    }
}

Async hooks

---

Query: {
    users: {
        resolve: () => { ... },
        post: async (result) => {
            await updateAudit(result)
        }
    }
}

Pre Hook

---

type PreHook = (
    root: any,
    args: { [k: string]: any },
    context: Context,
    info: DocumentNode
) => void;

Resolve Hook

---

type Resolve = (
    root: any,
    args: { [k: string]: any },
    context: Context,
    info: DocumentNode
) => void;

Post Hook

---

type PostHook = (
    resolve: any,
    root: any,
    args: { [k: string]: any },
    context: Context,
    info: DocumentNode
) => void;