Optional declaration with ? suffix in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an optional integer variable.

Swift

var age: Int[1]

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

A!

B?

C:

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using ! instead of ? to declare an optional

Using : or = which are not for optional declaration

In Swift, adding a ? after the type declares an optional variable.

2fill in blank

medium

Complete the code to declare an optional string variable named name.

Swift

var name: String[1]

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

A!

B:

C=

D?

Attempts:

3 left

💡 Hint

Common Mistakes

Using ! which means forced unwrapping, not declaration

Using : or = which are not for optional declaration

The ? suffix after String makes name an optional string.

3fill in blank

hard

Fix the error in the optional declaration of a Double variable.

Swift

var price: Double[1]

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

A:

B!

C?

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using : which is for type annotation but not optional

Using ! which is for forced unwrapping

Use ? to declare price as an optional Double.

4fill in blank

hard

Fill both blanks to declare an optional Boolean variable and assign nil.

Swift

var isActive: Bool[1] = [2]

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

A?

Btrue

Cnil

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning true or false instead of nil to an optional

Using ! instead of ? for optional declaration

Use ? to declare optional and assign nil to show no value.

5fill in blank

hard

Fill all three blanks to declare an optional string variable, assign nil, and then assign a value.

Swift

var city: String[1] = [2]
city = [3]

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

A?

Bnil

C"Paris"

D"London"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using ? for optional declaration

Assigning a string value directly without optional

Using wrong quotes or missing quotes around string

Declare city as optional with ?, assign nil, then assign a string value.