[Solved] You are designing a GraphQL schema where each Student has exactly one Locker, and each Locker is assigned to exactly one... How should you define the types to enforce this one-to-one relationship? | GraphQL

GraphQL - Type Relationships

You are designing a GraphQL schema where each Student has exactly one Locker, and each Locker is assigned to exactly one Student. How should you define the types to enforce this one-to-one relationship?

Atype Student { id: ID! locker: Locker! } type Locker { id: ID! student: Student! }

Btype Student { id: ID! lockers: [Locker]! } type Locker { id: ID! student: Student }

Ctype Student { id: ID! locker: Locker } type Locker { id: ID! }

Dtype Student { id: ID! lockerId: ID! } type Locker { id: ID! studentId: ID! }

Step-by-Step Solution

Solution:

Step 1: Identify one-to-one enforcement
Both sides must reference each other with non-nullable fields to enforce exactly one relation.
Step 2: Evaluate options
type Student { id: ID! locker: Locker! } type Locker { id: ID! student: Student! } uses non-nullable fields on both types, enforcing one-to-one. type Student { id: ID! lockers: [Locker]! } type Locker { id: ID! student: Student } uses lists or nullable fields, allowing multiple or optional relations. type Student { id: ID! locker: Locker } type Locker { id: ID! } omits back reference. type Student { id: ID! lockerId: ID! } type Locker { id: ID! studentId: ID! } uses scalar IDs without object references.
Final Answer:
type Student { id: ID! locker: Locker! } type Locker { id: ID! student: Student! } -> Option A
Quick Check:
Non-nullable mutual references enforce one-to-one [OK]

Quick Trick: Use non-nullable mutual object references for one-to-one [OK]

Common Mistakes:

Using lists instead of single object fields
Making fields nullable, allowing zero or many
Using scalar IDs instead of object types

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How should you define the types to enforce this one-to-one relationship?

Step 1: Identify one-to-one enforcement

Step 2: Evaluate options

Final Answer:

Quick Check:

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