Why Swift loops are safe by default - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a safe loop that iterates over an array.

Swift

let numbers = [1, 2, 3, 4, 5]
for number in [1] {
    print(number)
}

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

Anumbers

B0..<5

C1...5

DArray(1...5)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a range instead of the array variable causes errors or unexpected behavior.

Using the array name directly in the loop ensures safe iteration over its elements.

2fill in blank

medium

Complete the code to safely iterate over the indices of an array.

Swift

let fruits = ["Apple", "Banana", "Cherry"]
for index in [1] {
    print(fruits[index])
}

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A1...fruits.count

B0..<fruits.count

C0...fruits.count

D1..<fruits.count

Attempts:

3 left

💡 Hint

Common Mistakes

Using a closed range causes an index out of range error.

Using 0..

3fill in blank

hard

Fix the error in the loop to prevent out-of-bounds access.

Swift

let letters = ["a", "b", "c"]
for i in 0...[1] {
    print(letters[i])
}

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Aletters.count - 1

Bletters.count - 2

Cletters.count + 1

Dletters.count

Attempts:

3 left

💡 Hint

Common Mistakes

Using letters.count causes a runtime error due to invalid index.

The last valid index is letters.count - 1; using this prevents out-of-bounds errors.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that filters keys with values greater than 10.

Swift

let data = ["a": 5, "b": 15, "c": 20]
let filtered = data.filter { $0.[1] > [2] }

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Avalue

B10

Ckey

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using $0.key instead of $0.value causes wrong filtering.

Accessing the value with $0.value and comparing it to 10 filters correctly.

5fill in blank

hard

Fill all three blanks to create a safe loop that prints uppercase keys with values less than 50.

Swift

let scores = ["math": 45, "science": 55, "english": 40]
for ([1], [2]) in scores {
    if [3] < 50 {
        print([1].uppercased())
    }
}

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Asubject

Bscore

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names or using incorrect comparisons causes errors.

Using (subject, score) and checking score < 50 prints uppercase subject names safely.