Optional chaining with ?. in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to safely access the street name using optional chaining.

Swift

let streetName = person.address[1]street

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

A?.

B!

C.

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' instead of '?.' causes a compile error if the optional is nil.

Using '!' forces unwrapping and can cause runtime crashes.

Using '?.' allows safe access to street property if address is not nil.

2fill in blank

medium

Complete the code to call the optional method safely using optional chaining.

Swift

let result = person.delegate[1]performAction()

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

A!

B?.

C->

D.

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' causes compile error if delegate is nil.

Using '!' can cause runtime crash if delegate is nil.

Optional chaining with '?.' safely calls the method if delegate is not nil.

3fill in blank

hard

Fix the error in safely accessing the nested optional property.

Swift

let zipCode = person.address[1]postalCode[2]code

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

A?.

B.

C!

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' for the first optional causes compile error.

Using '!' can cause runtime crash if optional is nil.

Use optional chaining for the first optional, then normal dot for non-optional property.

4fill in blank

hard

Fill both blanks to safely access the city name from an optional nested property.

Swift

let city = person[1]address[2]city

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

A?.

B.

C!

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' for the optional property causes errors.

Using '!' risks runtime crashes if the optional is nil.

Use optional chaining for the first optional property, then dot for the non-optional city.

5fill in blank

hard

Fill all three blanks to safely call a method on an optional delegate's optional property.

Swift

let value = person[1]delegate[2]optionalProperty[3]computeValue()

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

A?.

B.

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!' can cause runtime crashes if any optional is nil.

Using '.' for optional properties causes compile errors.

Use optional chaining for optional delegate and optionalProperty, dot for non-optional property.