Shared types across subgraphs in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a shared type in a subgraph schema.

GraphQL

type Product @key(fields: "id") {
  id: ID! 
  name: String! 
  [1]: Float
}

Drag options to blanks, or click blank then click option'

Aprice

Bweight

Cdescription

Dcategory

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a field that is not numeric like 'name' or 'category'.

Leaving the field blank.

The price field is commonly shared across subgraphs to represent product cost.

2fill in blank

medium

Complete the code to extend a shared type in another subgraph.

GraphQL

extend type Product @key(fields: "id") {
  id: ID! 
  [1]: String
}

Drag options to blanks, or click blank then click option'

Aweight

Bmanufacturer

Cprice

Dstock

Attempts:

3 left

💡 Hint

Common Mistakes

Using fields already defined in the base type like 'price'.

Choosing numeric fields instead of descriptive text.

The manufacturer field is often added in an extension to provide additional product details.

3fill in blank

hard

Fix the error in the shared type definition by completing the directive.

GraphQL

type User @[1](fields: "id") {
  id: ID! 
  username: String!
}

Drag options to blanks, or click blank then click option'

Akey

Bexternal

Cprovides

Drequires

Attempts:

3 left

💡 Hint

Common Mistakes

Using @external which is for fields, not types.

Using @provides or @requires which are for field-level directives.

The @key directive marks the primary key field for the shared type.

4fill in blank

hard

Fill both blanks to correctly mark a field as shared and external.

GraphQL

extend type Review @key(fields: "id") {
  id: ID! 
  username: String @[1] @[2]
}

Drag options to blanks, or click blank then click option'

Aexternal

Bprovides

Drequires

Attempts:

3 left

💡 Hint

Common Mistakes

Using @provides or @requires instead of @external.

Not marking the field as external when extending.

The username field is marked as external to indicate it is defined in another subgraph.

5fill in blank

hard

Fill all three blanks to define a shared type with a key and external field.

GraphQL

type Product @[1](fields: "id") {
  id: ID! 
  name: String!
  price: Float @[2] @[3]
}

Drag options to blanks, or click blank then click option'

Akey

Bexternal

Dprovides

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing @provides with @external.

Not marking the key directive correctly.

The @key directive marks the primary key. The price field is marked external to indicate it is shared from another subgraph.

Practice

1. What is the main purpose of using @key in shared types across GraphQL subgraphs?

easy

A. To mark fields that uniquely identify an entity across subgraphs

B. To define a field as optional in the schema

C. To specify the data type of a field

D. To mark a field as deprecated

Solution

1. Step 1: Understand the role of @key

   The @key directive marks fields that uniquely identify an entity across subgraphs, enabling them to share the same type.

2. Step 2: Differentiate from other directives

   Other directives like @external or @deprecated serve different purposes, not unique identification.

3. Final Answer:

   To mark fields that uniquely identify an entity across subgraphs -> Option A

4. Quick Check:

   @key marks unique identifiers [OK]

Hint: Remember: @key means unique ID for shared types [OK]

Common Mistakes:

• Confusing @key with @external
• Thinking @key marks optional fields
• Assuming @key defines data types

2. Which of the following is the correct way to mark a field as coming from another subgraph in a shared type?

easy

A. Use @key directive on the field

B. Use @provides directive on the field

C. Use @requires directive on the field

D. Use @external directive on the field

Solution

1. Step 1: Identify the directive for external fields

   The @external directive marks fields that are owned by another subgraph but referenced in the current one.

2. Step 2: Differentiate from other directives

   @key marks unique identifiers, @requires and @provides relate to field dependencies, not external ownership.

3. Final Answer:

   Use @external directive on the field -> Option D

4. Quick Check:

   @external marks fields from other subgraphs [OK]

Hint: External fields use @external directive [OK]

Common Mistakes:

• Using @key instead of @external
• Confusing @requires with @external
• Not marking external fields at all

3. Given the following subgraph schema snippet:

type Product @key(fields: "id") {
  id: ID!
  name: String
  price: Float @external
}

Which statement is true about the price field?

medium

A. It is defined and owned by this subgraph

B. It is a unique identifier for Product

C. It is defined in another subgraph and referenced here

D. It is deprecated and should not be used

Solution

1. Step 1: Analyze the @external directive on price

   The @external directive means price is not owned here but comes from another subgraph.

2. Step 2: Understand the role of @key on id

   The id field is the unique identifier, so price is not an ID.

3. Final Answer:

   It is defined in another subgraph and referenced here -> Option C

4. Quick Check:

   @external means field is from another subgraph [OK]

Hint: Fields with @external come from other subgraphs [OK]

Common Mistakes:

• Thinking @external means field is owned here
• Confusing @key with @external
• Assuming @external means deprecated

4. Consider this subgraph type definition:

type User @key(fields: "userId") {
  userId: ID!
  email: String @external
  name: String
}

Which statement is true about the email field?

medium

A. It is defined in another subgraph and referenced here

B. The @key directive must include email field

C. The userId field cannot be used as a key

D. The name field must be marked @external

Solution

1. Step 1: Analyze the @external directive on email

   The @external directive means email is defined in another subgraph and referenced here.

2. Step 2: Differentiate from other fields

   userId is the @key field provided locally, name is owned locally (no directive).

3. Final Answer:

   It is defined in another subgraph and referenced here -> Option A

4. Quick Check:

   @external means field from another subgraph [OK]

Hint: @external means field from another subgraph [OK]

Common Mistakes:

• Thinking @external means owned locally
• Believing @key must include all fields
• Assuming all fields need @external

5. You have two subgraphs sharing a Book type. Subgraph A defines:

type Book @key(fields: "isbn") {
  isbn: ID!
  title: String
}

Subgraph B defines:

extend type Book @key(fields: "isbn") {
  isbn: ID! @external
  author: String
}

Which statement best describes how these shared types work together?

hard

A. Both subgraphs own isbn, causing a conflict

B. Subgraph A owns isbn and title, Subgraph B extends Book using isbn as key and adds author

C. Subgraph B owns isbn and author, Subgraph A only references isbn

D. Subgraph B cannot extend Book without redefining title

Solution

1. Step 1: Identify ownership of fields

   Subgraph A defines Book with isbn and title, so it owns these fields.

2. Step 2: Understand extension in Subgraph B

   Subgraph B extends Book, marking isbn as @external (owned by A) and adds author.

3. Step 3: Confirm no conflicts

   Using @key with the same field isbn allows both subgraphs to share the type without conflict.

4. Final Answer:

   Subgraph A owns isbn and title, Subgraph B extends Book using isbn as key and adds author -> Option B

5. Quick Check:

   Extension uses @external keys to share types [OK]

Hint: Extension uses @external keys to share types [OK]

Common Mistakes:

• Thinking both subgraphs own the same key field
• Believing extension requires redefining all fields
• Assuming conflicts occur with shared keys