Nil coalescing operator (??) in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to provide a default value using the nil coalescing operator.

Swift

let name: String? = nil
let displayName = name [1] "Guest"
print(displayName)

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

A??

B||

C&&

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using logical operators like || or && instead of the nil coalescing operator.

Using the force unwrap operator ! which can cause a crash if the value is nil.

The nil coalescing operator ?? returns the value on its left if it is not nil; otherwise, it returns the value on its right.

2fill in blank

medium

Complete the code to safely unwrap the optional and provide a default integer value.

Swift

var optionalNumber: Int? = nil
let number = optionalNumber [1] 10
print(number)

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

A!

B??

C&&

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using force unwrap ! which can cause runtime errors if nil.

Using logical operators which do not work with optionals.

The nil coalescing operator ?? unwraps the optional if it has a value; otherwise, it uses the default value on the right.

3fill in blank

hard

Fix the error in the code by using the correct operator to provide a default string.

Swift

let optionalGreeting: String? = nil
let greeting = optionalGreeting [1] "Hello, World!"
print(greeting)

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

A!

B+

C??

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using ! which can cause a crash if the optional is nil.

Using operators like + or && which are not for unwrapping optionals.

The nil coalescing operator ?? is the correct way to provide a default value when the optional is nil.

4fill in blank

hard

Fill in the blank to use the nil coalescing operator to provide default values.

Swift

let scores: [String: Int?] = ["Alice": 85, "Bob": nil, "Charlie": 92]
let finalScores = scores.mapValues { $0 [1] 0 }
print(finalScores)

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

A??

B!

Attempts:

3 left

💡 Hint

Common Mistakes

Using force unwrap ! which can cause runtime errors.

Using logical operators like || or &&.

The nil coalescing operator ?? provides a default value of 0 when the optional is nil.

5fill in blank

hard

Fill all three blanks to create a dictionary that maps names to their uppercase keys and uses the nil coalescing operator to provide default scores greater than zero.

Swift

let rawScores: [String: Int?] = ["dave": nil, "emma": 75, "frank": nil]
let processedScores = [[1]: [2] for (name, score) in rawScores if ([2] [3] 0)]
print(processedScores)

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

Aname.uppercased()

Bscore ?? 0

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using raw name instead of uppercase for keys.

Not using nil coalescing operator to handle nil scores.

Using wrong comparison operator in the filter.

The key is the uppercase version of the name, the value uses ?? to provide 0 if score is nil, and the filter keeps only scores greater than 0.