Scalar types (String, Int, Float, Boolean, ID) in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a GraphQL field that returns a string.

GraphQL

type Query { greeting: [1] }

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

AInt

BBoolean

CString

DFloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int or Float for text fields.

Confusing Boolean with String.

The String scalar type is used to represent text in GraphQL.

2fill in blank

medium

Complete the code to define a GraphQL field that returns an integer.

GraphQL

type Query { age: [1] }

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

AInt

BBoolean

CFloat

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using Float instead of Int for whole numbers.

Using String for numeric values.

The Int scalar type is used for whole numbers in GraphQL.

3fill in blank

hard

Fix the error in the code by choosing the correct scalar type for a price field that can have decimals.

GraphQL

type Product { price: [1] }

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

ABoolean

BFloat

CInt

DID

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int which only supports whole numbers.

Using Boolean or ID for numeric values.

The Float scalar type is used for numbers with decimals in GraphQL, such as prices.

4fill in blank

hard

Fill both blanks to define a GraphQL type with a Boolean field and an ID field.

GraphQL

type User { isActive: [1] id: [2] }

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

ABoolean

BString

CID

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of Boolean for true/false.

Using Int instead of ID for unique identifiers.

Boolean is used for true/false values, and ID is used for unique identifiers in GraphQL.

5fill in blank

hard

Fill all three blanks to define a GraphQL type with a String name, an Int age, and a Boolean isMember field.

GraphQL

type Member { name: [1] age: [2] isMember: [3] }

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

ABoolean

BInt

CString

DFloat

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up Int and Float for age.

Using Boolean for name or age fields.

String is for text like names, Int for whole numbers like age, and Boolean for true/false values like membership status.

Practice

1. Which of the following is NOT a standard GraphQL scalar type?

easy

A. Boolean

B. String

C. Date

D. ID

Solution

1. Step 1: Recall standard GraphQL scalar types

   The standard scalar types are String, Int, Float, Boolean, and ID.

2. Step 2: Identify the non-standard type

   Date is not a built-in scalar type in GraphQL; it requires a custom scalar.

3. Final Answer:

   Date -> Option C

4. Quick Check:

   Standard scalars exclude Date [OK]

Hint: Remember only 5 built-in scalars: String, Int, Float, Boolean, ID [OK]

Common Mistakes:

• Thinking Date is built-in
• Confusing ID with Int
• Assuming Boolean is custom

2. Which of the following is the correct way to declare a field of type ID in a GraphQL schema?

easy

A. userId: id

B. userId: Int

C. userId: String!

D. userId: ID!

Solution

1. Step 1: Understand GraphQL type syntax

   Types are case-sensitive; ID must be uppercase and non-null indicated by !.

2. Step 2: Check each option

   userId: ID! uses correct type 'ID!' with uppercase and non-null. Others are either lowercase or wrong type.

3. Final Answer:

   userId: ID! -> Option D

4. Quick Check:

   ID type is uppercase and non-null with ! [OK]

Hint: ID type is uppercase and ! means non-null [OK]

Common Mistakes:

• Using lowercase 'id'
• Confusing ID with String
• Omitting ! for required fields

3. Given this GraphQL query result for a field declared as Float:
{ price: 19 }
What is the actual type of the returned value?

medium

A. Float

B. String

C. Integer

D. Boolean

Solution

1. Step 1: Understand GraphQL Float type

   Float represents decimal numbers but can also return whole numbers as floats.

2. Step 2: Analyze the value 19

   Even though 19 looks like an integer, GraphQL returns it as a Float type because the field is Float.

3. Final Answer:

   Float -> Option A

4. Quick Check:

   Float fields return numbers as floats, even whole numbers [OK]

Hint: Float fields always return float type, even if whole number [OK]

Common Mistakes:

• Assuming 19 is Integer
• Thinking Float must have decimal point
• Confusing with String

4. Identify the error in this GraphQL schema snippet:

type Product {
  id: ID
  name: String!
  price: float
  inStock: Boolean
}

medium

A. 'Boolean' should be lowercase 'boolean'

B. 'float' should be 'Float' with uppercase F

C. 'ID' should be 'Id' with lowercase d

D. 'String!' should be 'String' without exclamation mark

Solution

1. Step 1: Check scalar type capitalization

   GraphQL scalar types are case-sensitive; 'Float' must be capitalized.

2. Step 2: Verify other types

   'Boolean' and 'ID' are correctly capitalized; 'String!' is valid for non-null.

3. Final Answer:

   'float' should be 'Float' with uppercase F -> Option B

4. Quick Check:

   Scalar types must be capitalized exactly [OK]

Hint: Scalar types always start with uppercase letter [OK]

Common Mistakes:

• Using lowercase scalar types
• Changing Boolean case
• Removing ! from non-null

5. You want to store a unique identifier for users that is a string but should never be null. Which scalar type and modifier combination is best in GraphQL schema?

hard

A. ID!

B. String

C. Int!

D. Boolean!

Solution

1. Step 1: Understand the purpose of ID scalar

   ID is designed for unique identifiers and is serialized as string.

2. Step 2: Ensure non-null constraint

   Adding ! means the field cannot be null, which fits the requirement.

3. Final Answer:

   ID! -> Option A

4. Quick Check:

   Use ID! for unique, non-null string identifiers [OK]

Hint: Use ID! for unique, required string IDs [OK]

Common Mistakes:

• Using String without !
• Using Int for string IDs
• Using Boolean for IDs