Why let and var distinction matters in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a constant in Swift.

Swift

let number = [1]

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

A10

Bvar

Clet

D"ten"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' instead of a value

Assigning a string instead of a number

In Swift, let declares a constant, so you assign a value like 10 to it.

2fill in blank

medium

Complete the code to declare a variable in Swift.

Swift

var name = [1]

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

A10

Bvar

Clet

D"Alice"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let' instead of a value

Assigning a number instead of a string

Variables declared with var can change. Here, name is set to the string "Alice".

3fill in blank

hard

Fix the error in the code by choosing the correct keyword to allow changing the value.

Swift

[1] score = 5
score = 10

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

Ascore

B10

Cvar

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'let'

Choosing a value like '10' instead of the keyword

Choosing 'score'

The error occurs because let creates a constant that cannot be reassigned. Use var to declare a variable that can be changed.

4fill in blank

hard

Choose the keyword that allows mutating the array by appending an element.

Swift

[1] scores = [85, 90]
scores.append(95)

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

Alet

Bvar

Cconstant

Dfinal

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'let'

Using non-Swift keywords like 'constant'

let makes the array a constant and prevents mutating methods like append. Use var to declare mutable arrays.

5fill in blank

hard

Choose the keyword that allows the function to modify the counter.

Swift

[1] counter = 0

func incrementCounter() {
  counter += 1
}

incrementCounter()
print(counter)

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

Avar

Bstatic let

Clet

Dprivate var

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'let'

Adding unnecessary modifiers like 'static' or 'private'

To modify counter from within the function, declare it with var. Constants declared with let cannot be changed.