[Solved] This GraphQL schema snippet causes an error:type Post { id: ID! author: User } type User { id: ID! posts: [Post!]! }What is the likely cause? | GraphQL

GraphQL - Type Relationships

This GraphQL schema snippet causes an error:

type Post { id: ID! author: User } type User { id: ID! posts: [Post!]! }

What is the likely cause?

Aauthor field should be non-nullable (User!) to match posts list

Bposts field should be a single Post, not a list

CID fields must be strings, not ID type

DUser type is missing a required field

Step-by-Step Solution

Solution:

Step 1: Check author field nullability
Author is nullable (User), but posts list is non-nullable.
Step 2: Match nullability for consistency
Author should be non-nullable (User!) to ensure every Post has an author.
Final Answer:
author field should be non-nullable (User!) to match posts list -> Option A
Quick Check:
Nullability must be consistent in relationships [OK]

Quick Trick: Match nullability on both sides of relationship [OK]

Common Mistakes:

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This GraphQL schema snippet causes an error: