Lifecycle hooks

Hooks let you “hook into” Prisma-AppSync lifecycle to either trigger custom business logic or manipulate data at runtime.

👉 Example code

Basic example:

return await prismaAppSync.resolve({
    event,
    hooks: {
        // Mutate Post title before creation on database
        'before:createPost': async (params: BeforeHookParams) => {
            params.prismaArgs.data.title = 'New post title'
            return params
        },
        // Override query result using always the same Post title
        'after:listPosts': async (params: AfterHookParams) => {
            params.result = params.result.map(r => r.title = 'Always the same title')
            return params
        },
    },
})

Advanced example:

return await prismaAppSync.resolve<'likePost'>({
    event,
    hooks: {
        // execute before any query
        'before:**': async (params: BeforeHookParams) => params,

        // execute after any query
        'after:**': async (params: AfterHookParams) => params,

        // execute after custom resolver query `likePost`
        // (e.g. `query { likePost(postId: 3) }`)
        'after:likePost': async (params: AfterHookParams) => {
            await params.prismaClient.notification.create({
                data: {
                    event: 'POST_LIKED',
                    targetId: params.args.postId,
                    userId: params.authIdentity.sub,
                },
            })
            return params
        },
    },
})

👉 Types

export interface QueryParams {
    type: GraphQLType
    operation: string
    context: Context
    fields: string[]
    paths: string[]
    args: any
    prismaArgs: PrismaArgs
    authorization: Authorization
    identity: Identity
    headers: any
    prismaClient: PrismaClient
}

type BeforeHookParams = QueryParams

type AfterHookParams = QueryParams & {
    result: any | any[]
}

👉 Usage rules

• Hooks are made of a Path (e.g. after:updatePost) and an async function.

• Path syntax always starts with before: or after:.

  before or after querying data from the database.

• Path syntax after : uses Micromatch syntax.

• Hooks are fully typed, so VSCode IntelliSense will give you the full list of Hooks Paths you can use while typing. Example:

• Hooks functions all receive a single object as a parameter. Here is an example object received inside after:getPost:

{
    "type": "Query",
    "operation": "getPost",
    "context": { "action": "get", "alias": "access", "model": "Post" },
    "fields": ["title", "status"],
    "paths": ["get/post/title", "get/post/status"],
    "args": { "where": { "id": 5 } },
    "prismaArgs": {
        "where": { "id": 5 },
        "select": { "title": true, "status": true }
    },
    "authorization": "API_KEY",
    "identity": {},
    "result": { "title": "My first post", "status": "PUBLISHED" }
}

• Key result is only available inside after hooks.
• Hooks async functions MUST return the object received as a parameter (either mutated or untouched).
• Using hooks on custom resolvers requires explicitly listing resolvers using a TypeScript Generic prismaAppSync.resolve<T>:

// Using custom resolver `likePost`
return await prismaAppSync.resolve<'likePost'>({ event, hooks })

// Using multiple custom resolvers
return await prismaAppSync.resolve<'likePost' | 'unlikePost'>({ event, hooks })