List types in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a list of integers in GraphQL schema.

GraphQL

type Query { numbers: [[1]] }

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

AString

BInt

CBoolean

DFloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of Int for a list of numbers.

Forgetting to use square brackets for list types.

The list type in GraphQL is defined by wrapping the type in square brackets. Here, Int is the correct scalar type for integers.

2fill in blank

medium

Complete the code to define a list of non-nullable strings in GraphQL schema.

GraphQL

type Query { names: [[1]!] }

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

AInt

BBoolean

CString

DFloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int instead of String for text lists.

Placing the exclamation mark outside the brackets instead of after the type.

The exclamation mark ! after the type means the list elements cannot be null. Here, String is the correct scalar type for text.

3fill in blank

hard

Fix the error in the list type definition to make the list itself non-nullable but allow nullable elements.

GraphQL

type Query { items: [1] }

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

AString

BString!

C[String!]

D[String]!

Attempts:

3 left

💡 Hint

Common Mistakes

Putting exclamation mark after the type instead of after the list.

Using String! without brackets which is not a list.

To make the list non-nullable but allow nullable elements, place the exclamation mark after the closing bracket: [String]!.

4fill in blank

hard

Fill both blanks to define a list of non-nullable integers where the list itself is also non-nullable.

GraphQL

type Query { scores: [1][2] }

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

A[

BInt!

C]!

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Placing exclamation marks in the wrong positions.

Forgetting to wrap the type in brackets.

The correct syntax for a non-nullable list of non-nullable integers is [Int!]!. The list is wrapped in brackets with exclamation marks after the type and after the brackets.

5fill in blank

hard

Fill both blanks to define a GraphQL input type with a field that is a non-nullable list of nullable floats.

GraphQL

input FilterInput { values: [1][2] }

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

A[

BFloat

C]!

DFloat!

Attempts:

3 left

💡 Hint

Common Mistakes

Using Float! inside the list which makes elements non-nullable.

Placing exclamation mark after the type instead of after the brackets.

The field values is a non-nullable list (] followed by !) of nullable floats (Float without exclamation mark). So the correct syntax is [Float]!.

Practice

1. What does a list type in GraphQL represent?
[Int] means a list of what?

easy

A. A string value

B. A single integer

C. A collection of integers

D. A boolean value

Solution

1. Step 1: Understand list notation in GraphQL

   Square brackets [] indicate a list type that holds multiple values of the same type.

2. Step 2: Interpret [Int]

   This means a list containing zero or more integers.

3. Final Answer:

   A collection of integers -> Option C

4. Quick Check:

   List type = multiple values [OK]

Hint: Square brackets mean list of that type [OK]

Common Mistakes:

• Thinking it holds a single value
• Confusing list with string or boolean
• Ignoring the brackets meaning

2. Which of the following is the correct syntax to define a list of strings in GraphQL?

easy

A. string[]

B. [String]

C. (String[])

D. {String}

Solution

1. Step 1: Recall GraphQL list syntax

   GraphQL uses square brackets [] around a type to define a list.

2. Step 2: Identify correct option

   [String] is the correct way to define a list of strings in GraphQL.

3. Final Answer:

   [String] -> Option B

4. Quick Check:

   List syntax = brackets around type [OK]

Hint: Use square brackets around type for lists [OK]

Common Mistakes:

• Using language-specific syntax like string[]
• Using parentheses or curly braces instead of brackets
• Missing brackets entirely

3. Given this GraphQL schema snippet:

type Query {
  favoriteNumbers: [Int]
}

What is a valid response for favoriteNumbers?

medium

A. {1, 2, 3}

B. 42

C. "[1, 2, 3]"

D. [1, 2, 3]

Solution

1. Step 1: Understand the field type

   favoriteNumbers is a list of integers, so the response must be a list (array) of numbers.

2. Step 2: Check each option

   [1, 2, 3] is a list of integers. 42 is a single integer, not a list. "[1, 2, 3]" is a string, not a list. {1, 2, 3} uses curly braces which is invalid syntax.

3. Final Answer:

   [1, 2, 3] -> Option D

4. Quick Check:

   List field returns list value [OK]

Hint: List fields return arrays, not single values [OK]

Common Mistakes:

• Returning a single value instead of a list
• Returning a string instead of a list
• Using wrong brackets for lists

4. Identify the error in this GraphQL list type declaration:

type User {
  tags: [String
}

medium

A. Missing closing bracket "]" for the list type

B. List types cannot hold strings

C. Square brackets should be replaced with parentheses

D. Field name cannot be "tags"

Solution

1. Step 1: Check list type syntax

   List types require both opening and closing square brackets around the type.

2. Step 2: Locate syntax error

   The closing bracket "]" is missing after String, causing a syntax error.

3. Final Answer:

   Missing closing bracket "]" for the list type -> Option A

4. Quick Check:

   List syntax needs matching brackets [OK]

Hint: Always close brackets in list types [OK]

Common Mistakes:

• Forgetting the closing bracket
• Using wrong brackets like parentheses
• Thinking list can't hold strings

5. You want to define a GraphQL field that can return null or a list of non-null integers, but the list itself can be empty. Which type declaration is correct?

hard

A. [Int!]

B. [Int]!

C. [Int!]!

D. Int!

Solution

1. Step 1: Understand non-null and list syntax

   Int! means non-null integer, [Int!] means list of non-null integers, list itself can be null or empty.

2. Step 2: Analyze options

   [Int!]: List of non-null integers, list nullable (can be empty).[Int]!: Non-null list of nullable integers.[Int!]!: Non-null list of non-null integers (list cannot be null).Int!: Single non-null integer, not a list.

3. Final Answer:

   [Int!] -> Option A

4. Quick Check:

   Non-null items inside nullable list = [Int!] [OK]

Hint: Non-null items inside list use [Type!] [OK]

Common Mistakes:

• Making list itself non-null when it should be nullable
• Confusing non-null item vs non-null list
• Using single type instead of list