Extensions with constraints in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to extend Array only when its elements conform to Equatable.

Swift

extension Array where Element: [1] {
    func containsElement(_ element: Element) -> Bool {
        return self.contains(element)
    }
}

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

AHashable

BComparable

CEquatable

DCodable

Attempts:

3 left

💡 Hint

Common Mistakes

Using a protocol that doesn't support equality checking like Comparable.

Forgetting to add the constraint after 'where Element:'.

The extension applies only when the array's elements conform to Equatable, allowing use of the contains method.

2fill in blank

medium

Complete the code to add a method only for Dictionary where Key is String.

Swift

extension Dictionary where [1] == String {
    func allKeys() -> [String] {
        return Array(self.keys)
    }
}

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AKey

BElement

CSelf

DValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Value' instead of 'Key' in the constraint.

Using 'Element' which is not a dictionary type alias.

The extension applies only when the Key type of the dictionary is String.

3fill in blank

hard

Fix the error in the extension to add a method only when Element conforms to Numeric.

Swift

extension Array where Element: [1] {
    func sum() -> Element {
        return self.reduce(0, +)
    }
}

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ACodable

BComparable

CEquatable

DNumeric

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Comparable' which does not guarantee addition.

Using 'Equatable' which only supports equality checks.

The sum method requires elements to conform to Numeric so that addition and zero are defined.

4fill in blank

hard

Fill both blanks to extend Sequence only when Element is Hashable and add a method to get unique elements.

Swift

extension Sequence where [1]: [2] {
    func uniqueElements() -> [Element] {
        var seen = Set<Element>()
        return self.filter { seen.insert($0).inserted }
    }
}

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

AElement

BHashable

CEquatable

DComparable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Equatable' instead of 'Hashable' which is needed for Set.

Using 'Sequence' instead of 'Element' in the constraint.

The extension requires the Element to conform to Hashable so it can be stored in a Set to filter unique values.

5fill in blank

hard

Fill all three blanks to extend Optional only when Wrapped is Comparable and add a method to compare with another Optional.

Swift

extension Optional where [1]: [2] {
    func isGreater(than other: Optional<[3]>) -> Bool {
        switch (self, other) {
        case let (.some(a), .some(b)):
            return a > b
        default:
            return false
        }
    }
}

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

AWrapped

BComparable

DEquatable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Equatable' instead of 'Comparable' which does not support > operator.

Using 'Optional' instead of 'Wrapped' in the constraint.

The extension applies when Wrapped type conforms to Comparable. The method compares two optionals by unwrapping and comparing their values.