Why property wrappers reduce boilerplate in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a property wrapper named Capitalized.

Swift

propertyWrapper struct Capitalized {
    private var value: String = ""
    var wrappedValue: String {
        get { value }
        set { value = newValue[1] }
    }
}

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

A.lowercased()

B.capitalized

C.uppercased()

D.trimmingCharacters(in: .whitespaces)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method that changes case incorrectly, like lowercased or uppercased.

Forgetting to apply the method to the newValue.

The property wrapper modifies the new value by applying the capitalized method to reduce repetitive capitalization code.

2fill in blank

medium

Complete the code to apply the Capitalized property wrapper to the name property.

Swift

struct Person {
    @[1] var name: String
}

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ALowercased

BTrimmed

CCapitalized

DUppercased

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong wrapper name or forgetting the '@' symbol.

Confusing capitalization with other string transformations.

The @Capitalized wrapper is applied to the name property to automatically capitalize it.

3fill in blank

hard

Fix the error in the property wrapper by completing the missing initializer.

Swift

propertyWrapper struct Capitalized {
    private var value: String = ""
    var wrappedValue: String {
        get { value }
        set { value = newValue.capitalized }
    }
    init([1]) {
        self.wrappedValue = wrappedValue
    }
}

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AwrappedValue: String

Bvalue: String

CnewValue: String

DinitialValue: String

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name other than wrappedValue.

Not initializing the property wrapper's value properly.

The initializer must accept wrappedValue to initialize the property wrapper correctly.

4fill in blank

hard

Fill both blanks to create a property wrapper that trims whitespace and capitalizes the string.

Swift

propertyWrapper struct TrimmedCapitalized {
    private var value: String = ""
    var wrappedValue: String {
        get { value }
        set { value = newValue[1][2] }
    }
}

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A.trimmingCharacters(in: .whitespaces)

B.capitalized

C.lowercased()

D.uppercased()

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing the order of trimming and capitalization.

Using incorrect string methods.

First trim whitespace, then capitalize the string to reduce repetitive code.

5fill in blank

hard

Fill all three blanks to create a property wrapper that trims, capitalizes, and limits the string length to 10 characters.

Swift

propertyWrapper struct TrimCapLimit {
    private var value: String = ""
    var wrappedValue: String {
        get { value }
        set {
            let trimmed = newValue[1]
            let capitalized = trimmed[2]
            value = String(capitalized.prefix([3]))
        }
    }
}

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

A.trimmingCharacters(in: .whitespaces)

B.capitalized

C10

D.lowercased()

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong order of string methods.

Forgetting to convert prefix result back to String.

Using an incorrect limit number.

The code trims whitespace, capitalizes the string, and then limits it to 10 characters to reduce repetitive code.