Nil coalescing operator deep usage 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"

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 unwrap an optional integer and provide a default value using the nil coalescing operator.

Swift

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

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

A!

B?

C??

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using the force unwrap operator '!' which can cause runtime errors if the optional is nil.

Using the ternary conditional operator '?' incorrectly.

The '??' 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 correctly using the nil coalescing operator to provide a default string.

Swift

let optionalGreeting: String? = nil
let greeting = optionalGreeting [1] "Hello"

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

A==

B!

C?:

D??

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using comparison operators like '==' or ternary operators incorrectly.

The nil coalescing operator '??' is used to provide a default value when the optional is nil.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that uses 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] [2] }

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

A??

B0

Cnil

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using force unwrap '!' which can cause runtime errors.

Using 'nil' as a default value which defeats the purpose of providing a fallback.

The mapValues function uses '??' to unwrap the optional Int values, providing 0 as a default if nil.

5fill in blank

hard

Fill all three blanks to safely unwrap nested optionals using the nil coalescing operator.

Swift

struct User {
    var profile: Profile?
}
struct Profile {
    var nickname: String?
}

let user: User? = User(profile: Profile(nickname: nil))
let nickname = user[1]profile[2]nickname [3] "Anonymous"

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

A?->

B??

D?.

Attempts:

3 left

💡 Hint

Common Mistakes

Using force unwraps which can cause crashes if any optional is nil.

Confusing optional chaining syntax.

Use optional chaining with '?.' to safely access nested optionals, then use '??' to provide a default value.