Enum types in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this GraphQL enum query?

Given this GraphQL enum definition and query, what is the output?

enum Status {
  ACTIVE
  INACTIVE
  PENDING
}

type User {
  id: ID!
  name: String!
  status: Status!
}

query {
  user(id: "1") {
    name
    status
  }
}

Assume the user with id "1" has status ACTIVE.

A {"data": {"user": {"name": "Alice", "status": "ACTIVE"}}}

B {"data": {"user": {"name": "Alice", "status": "active"}}}

C {"data": {"user": {"name": "Alice", "status": 1}}}

D {"error": "Field 'status' is not defined"}

💡 Hint

Enum values in GraphQL are case sensitive and returned as defined.

The enum value is returned exactly as defined in the schema, in uppercase. So the status is "ACTIVE".

🧠 Conceptual

intermediate

Which statement about GraphQL enums is true?

Choose the correct statement about enums in GraphQL.

A Enum values must be unique and are case sensitive, usually uppercase without spaces.

B Enum values can be any string, including lowercase and spaces.

C Enum values can be numbers or booleans.

D Enum values are optional and can be omitted in queries.

💡 Hint

Think about how enums are defined and used in GraphQL schemas.

GraphQL enums must have unique names, are case sensitive, and typically use uppercase letters without spaces.

📝 Syntax

advanced

Identify the syntax error in this enum definition

Which option correctly fixes the syntax error in this GraphQL enum?

enum Color {
  RED
  GREEN
  BLUE
  LIGHT BLUE
}

A Add quotes around 'LIGHT BLUE'

B Replace 'LIGHT BLUE' with 'lightblue'

C Replace 'LIGHT BLUE' with 'LIGHT_BLUE'

D Remove 'LIGHT BLUE' entirely

💡 Hint

Enum values cannot contain spaces.

Enum values must be valid names without spaces. Using underscore is the correct fix.

🔧 Debug

advanced

Why does this GraphQL query fail with an enum argument?

Given this schema snippet:

enum Role {
  ADMIN
  USER
  GUEST
}

type Query {
  usersByRole(role: Role!): [User!]!
}

And this query:

query {
  usersByRole(role: "ADMIN") {
    id
    name
  }
}

Why does the query fail?

A The enum value ADMIN is not defined in the schema

B Enum arguments must be passed without quotes, like role: ADMIN

C The query must use lowercase enum values, like role: admin

D The argument role must be omitted because it is optional

💡 Hint

Think about how enum values are passed as arguments in GraphQL queries.

Enum values are passed without quotes in GraphQL queries. Passing "ADMIN" as a string causes an error.

❓ optimization

expert

Optimize this GraphQL schema using enums

You have a schema with a 'status' field as a string with possible values 'active', 'inactive', 'pending'. Which change optimizes the schema for better validation and clarity?

A Change 'status' to an integer representing each status

B Keep 'status' as a string but add comments listing possible values

C Remove 'status' field and use a boolean 'isActive' instead

D Change 'status' field type to an enum with values ACTIVE, INACTIVE, PENDING

💡 Hint

Enums help restrict values and improve schema clarity.

Using an enum for 'status' restricts allowed values and makes the schema clearer and safer.

Practice

1. What is the main purpose of using enum types in GraphQL schemas?

easy

A. To allow any string value for a field

B. To create a numeric range for a field

C. To define a list of objects

D. To restrict a field to a fixed set of allowed values

Solution

1. Step 1: Understand enum purpose

   Enums limit a field to specific predefined values, ensuring data consistency.

2. Step 2: Compare options

   Only To restrict a field to a fixed set of allowed values describes restricting values to a fixed set, which is the enum's role.

3. Final Answer:

   To restrict a field to a fixed set of allowed values -> Option D

4. Quick Check:

   Enum = fixed allowed values [OK]

Hint: Enums fix allowed values, not free text or ranges [OK]

Common Mistakes:

• Thinking enums allow any string
• Confusing enums with lists or objects
• Assuming enums define numeric ranges

2. Which of the following is the correct syntax to define an enum type Status with values ACTIVE and INACTIVE in GraphQL?

easy

A. enum Status: ACTIVE | INACTIVE

B. enum Status { ACTIVE INACTIVE }

C. enum Status = ["ACTIVE", "INACTIVE"]

D. type Status = enum { ACTIVE, INACTIVE }

Solution

1. Step 1: Recall GraphQL enum syntax

   GraphQL enums are defined using enum Name { VALUE1 VALUE2 } syntax.

2. Step 2: Check each option

   enum Status { ACTIVE INACTIVE } matches the correct syntax. Others use invalid or mixed syntax.

3. Final Answer:

   enum Status { ACTIVE INACTIVE } -> Option B

4. Quick Check:

   Correct enum syntax = enum Status { ACTIVE INACTIVE } [OK]

Hint: Enums use curly braces with values, no equals or brackets [OK]

Common Mistakes:

• Using equals sign or brackets for enums
• Confusing enum with type or array syntax
• Using colon or pipe symbols incorrectly

3. Given the enum definition:

enum Role { ADMIN USER GUEST }

and the query:

{ userRole }

where userRole returns ADMIN, what will be the output type of userRole?

medium

A. A boolean true

B. An integer representing ADMIN

C. "ADMIN" (a string matching enum value)

D. An error because ADMIN is not a string

Solution

1. Step 1: Understand enum value representation

   GraphQL enums return the enum value as a string matching one of the defined enum names.

2. Step 2: Analyze the query output

   The query returns ADMIN, which is output as the string "ADMIN".

3. Final Answer:

   "ADMIN" (a string matching enum value) -> Option C

4. Quick Check:

   Enum output = string value [OK]

Hint: Enum values output as strings, not numbers or booleans [OK]

Common Mistakes:

• Expecting numeric or boolean output
• Thinking enum values cause errors
• Confusing enum with custom object types

4. Consider this enum definition:

enum Color { RED GREEN BLUE }

Which of the following queries will cause a validation error?

medium

A. { favoriteColor(color: YELLOW) }

B. { favoriteColor(color: GREEN) }

C. { favoriteColor(color: RED) }

D. { favoriteColor(color: BLUE) }

Solution

1. Step 1: Check enum allowed values

   The enum Color allows only RED, GREEN, and BLUE.

2. Step 2: Identify invalid value

   { favoriteColor(color: YELLOW) } uses YELLOW, which is not in the enum, causing a validation error.

3. Final Answer:

   { favoriteColor(color: YELLOW) } -> Option A

4. Quick Check:

   Invalid enum value = validation error [OK]

Hint: Only use enum values defined exactly, others cause errors [OK]

Common Mistakes:

• Using values not in enum
• Ignoring case sensitivity in enum values
• Assuming enums accept any string

5. You want to add a new enum Priority with values LOW, MEDIUM, and HIGH to a GraphQL schema. You also want to ensure that a query tasksByPriority(priority: Priority) returns only tasks matching the selected priority. Which of the following schema snippets correctly defines the enum and query?

hard

A. enum Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] }

B. type Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] }

C. enum Priority = [LOW, MEDIUM, HIGH] type Query { tasksByPriority(priority: Priority): [Task] }

D. enum Priority { LOW, MEDIUM, HIGH } type Query { tasksByPriority(priority: Priority): Task }

Solution

1. Step 1: Define enum correctly

   enum Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] } uses correct enum syntax without commas: enum Priority { LOW MEDIUM HIGH }.

2. Step 2: Define query returning list of tasks

   The query returns a list [Task], matching multiple tasks by priority.

3. Step 3: Check other options

   type Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] } wrongly defines Priority as a type, not enum. enum Priority = [LOW, MEDIUM, HIGH] type Query { tasksByPriority(priority: Priority): [Task] } uses invalid enum syntax with equals and brackets. enum Priority { LOW, MEDIUM, HIGH } type Query { tasksByPriority(priority: Priority): Task } uses commas in enum and returns a single Task, not list.

4. Final Answer:

   enum Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] } -> Option A

5. Quick Check:

   Correct enum + list query = enum Priority { LOW MEDIUM HIGH } type Query { tasksByPriority(priority: Priority): [Task] } [OK]

Hint: Enums use braces without commas; queries return list with [Type] [OK]

Common Mistakes:

• Using commas inside enum definitions
• Defining enum as type instead of enum
• Returning single object instead of list for multiple results