Extending built-in types in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a method that returns the square of an Int.

Swift

extension Int {
    func squared() -> Int {
        return self [1] self
    }
}

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

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of * will add the number to itself, not square it.

Using - or / will cause incorrect results or errors.

The * operator multiplies the integer by itself to get the square.

2fill in blank

medium

Complete the code to add a computed property that returns the number of characters in a String.

Swift

extension String {
    var length: Int {
        return [1]
    }
}

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

Acount

Bself.length

Clength

Dself.count

Attempts:

3 left

💡 Hint

Common Mistakes

Using just count without self causes an error.

Using length is not a valid property in Swift strings.

self.count returns the number of characters in the string instance.

3fill in blank

hard

Fix the error in the extension that adds a method to check if an Int is even.

Swift

extension Int {
    func isEven() -> Bool {
        return self [1] 2 == 0
    }
}

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

A%

B/

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using division / instead of modulo causes a type mismatch.

Using multiplication or addition operators will not check evenness.

The modulo operator % returns the remainder. If remainder is 0 when divided by 2, the number is even.

4fill in blank

hard

Fill both blanks to create an extension that returns a new String with the first letter capitalized and the rest lowercase.

Swift

extension String {
    func capitalizedFirst() -> String {
        return self.prefix(1).[1]() + self.dropFirst().[2]()
    }
}

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

Auppercased

Blowercased

Ccapitalized

DtrimmingCharacters

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized() on the first letter only does not work.

Using trimmingCharacters() is unrelated to case changes.

uppercased() makes the first letter uppercase, and lowercased() makes the rest lowercase.

5fill in blank

hard

Fill all three blanks to create an extension that returns a dictionary with characters as keys and their counts as values, filtering only characters that appear more than once.

Swift

extension String {
    func repeatedCharacters() -> [Character: Int] {
        let counts = self.reduce(into: [:]) { counts, char in
            counts[char, default: [1]] += 1
        }
        return counts.filter { $0.value [2] [3] }
    }
}

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

A0

B>

C1

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing counts with 1 causes incorrect counts.

Using equality instead of greater than filters only characters appearing exactly once.

Initialize counts with 0, then filter characters with count greater than 1.