Nested resolver execution in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a nested resolver for the 'author' field inside 'Book' type.

GraphQL

const resolvers = {
  Book: {
    author: (parent, args, context, info) => [1]
  }
};

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Aargs.id

Bparent.authorId

Ccontext.db.getAuthorById(parent.authorId)

Dinfo.fieldName

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 'parent.authorId' directly without fetching author data.

Using 'args.id' which is not provided in this context.

The resolver for 'author' should fetch the author data using the 'authorId' from the parent 'Book' object, typically via a database call in context.

2fill in blank

medium

Complete the resolver to fetch nested comments for a 'Post' type.

GraphQL

const resolvers = {
  Post: {
    comments: (parent, args, context) => [1]
  }
};

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Acontext.db.getPostById(args.id)

Bparent.comments

Cargs.postId

Dcontext.db.getCommentsByPostId(parent.id)

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 'parent.comments' assuming comments are already loaded.

Using 'args.postId' which may not be provided.

The 'comments' resolver should fetch comments related to the post using the post's 'id' from the parent object.

3fill in blank

hard

Fix the error in the nested resolver to correctly fetch the 'profile' for a 'User'.

GraphQL

const resolvers = {
  User: {
    profile: (parent, args, context) => [1]
  }
};

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Acontext.db.getProfileByUserId(parent.id)

Bcontext.db.getProfileByUserId(args.id)

Cparent.profile

Dcontext.db.getUserById(parent.profileId)

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'args.id' which may not be passed to this resolver.

Returning 'parent.profile' assuming profile is already loaded.

The resolver should use the user's 'id' from the parent to fetch the profile. Using 'args.id' or 'parent.profile' is incorrect here.

4fill in blank

hard

Fill both blanks to correctly resolve nested 'orders' and their 'items' for a 'Customer'.

GraphQL

const resolvers = {
  Customer: {
    orders: (parent, args, context) => [1]
  },
  Order: {
    items: (parent, args, context) => [2]
  }
};

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Acontext.db.getOrdersByCustomerId(parent.id)

Bcontext.db.getItemsByOrderId(parent.id)

Cparent.orders

Dparent.items

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 'parent.orders' or 'parent.items' assuming data is preloaded.

Mixing up customer id and order id in the resolvers.

The 'orders' resolver fetches orders by customer id, and the 'items' resolver fetches items by order id from the parent object.

5fill in blank

hard

Fill all three blanks to correctly resolve nested 'categories', 'products', and 'reviews' in a GraphQL schema.

GraphQL

const resolvers = {
  Category: {
    products: (parent, args, context) => [1]
  },
  Product: {
    reviews: (parent, args, context) => [2]
  },
  Review: {
    author: (parent, args, context) => [3]
  }
};

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Acontext.db.getProductsByCategoryId(parent.id)

Bcontext.db.getReviewsByProductId(parent.id)

Ccontext.db.getUserById(parent.authorId)

Dparent.products

Attempts:

3 left

💡 Hint

Common Mistakes

Returning parent fields directly without fetching related data.

Using wrong parent properties like 'parent.productId' in the wrong resolver.

Each resolver fetches related data using the parent's id or authorId. Categories fetch products, products fetch reviews, and reviews fetch their author.