Custom validation property wrappers in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a property wrapper named ValidateNonEmpty that checks if a string is not empty.

Swift

import Foundation

@propertyWrapper
struct ValidateNonEmpty {
    private var value: String = ""

    var wrappedValue: String {
        get { value }
        set {
            if newValue.isEmpty {
                value = "[1]"
            } else {
                value = newValue
            }
        }
    }

    init(wrappedValue: String) {
        self.wrappedValue = wrappedValue
    }
}

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

A"invalid"

B"empty"

C"default"

D"none"

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the value empty instead of assigning a default invalid string.

Not handling the empty string case in the setter.

The property wrapper sets the value to "invalid" if the new string is empty, ensuring validation.

2fill in blank

medium

Complete the code to add a validation check that the wrapped string has at least 5 characters.

Swift

import Foundation

@propertyWrapper
struct ValidateLength {
    private var value: String = ""

    var wrappedValue: String {
        get { value }
        set {
            if newValue.count < [1] {
                value = "Too short"
            } else {
                value = newValue
            }
        }
    }

    init(wrappedValue: String) {
        self.wrappedValue = wrappedValue
    }
}

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

A3

B10

C5

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number smaller or larger than 5, which breaks the intended validation.

Confusing the comparison operator.

The validation requires the string to have at least 5 characters, so the check uses 5.

3fill in blank

hard

Fix the error in the property wrapper to correctly validate that the wrapped value is always uppercase.

Swift

import Foundation

@propertyWrapper
struct ValidateUppercase {
    private var value: String = ""

    var wrappedValue: String {
        get { value }
        set {
            if newValue == newValue.[1]() {
                value = newValue
            } else {
                value = newValue.uppercased()
            }
        }
    }

    init(wrappedValue: String) {
        self.wrappedValue = wrappedValue
    }
}

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

Alowercased

Bcapitalized

CtrimmingCharacters

Duppercased

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercased() which checks for lowercase instead.

Using capitalized() which capitalizes only the first letter.

To check if the string is uppercase, compare it to newValue.uppercased().

4fill in blank

hard

Fill both blanks to create a property wrapper that validates an integer is within a range 1 to 100.

Swift

import Foundation

@propertyWrapper
struct ValidateRange {
    private var value: Int = 1

    var wrappedValue: Int {
        get { value }
        set {
            if newValue [1] 1 && newValue [2] 100 {
                value = newValue
            } else {
                value = 1
            }
        }
    }

    init(wrappedValue: Int) {
        self.wrappedValue = wrappedValue
    }
}

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

A>=

B<=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or < which exclude boundary values.

Reversing the operators.

The validation checks if newValue is greater than or equal to 1 and less than or equal to 100.

5fill in blank

hard

Fill all three blanks to create a property wrapper that validates a string contains only letters and is capitalized.

Swift

import Foundation

@propertyWrapper
struct ValidateLettersCapitalized {
    private var value: String = ""

    var wrappedValue: String {
        get { value }
        set {
            let letters = CharacterSet.[1]
            if newValue.rangeOfCharacter(from: letters.inverted) == nil && newValue == newValue.[2]() {
                value = newValue
            } else {
                value = newValue.[3]()
            }
        }
    }

    init(wrappedValue: String) {
        self.wrappedValue = wrappedValue
    }
}

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

Aletters

Bcapitalized

Dlowercased

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong CharacterSet like alphanumerics.

Confusing capitalized() with uppercased().

Setting value to capitalized() instead of lowercased() on invalid input.

The code uses CharacterSet.letters to check only letters, compares with capitalized(), and sets value to lowercased() if invalid.