WrappedValue and projectedValue in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the wrapped value of the property wrapper.

Swift

struct User {
    @Logged var name: String

    func printName() {
        print(name[1])
    }
}

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

A.wrappedValue

B.projectedValue

C()

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Using .projectedValue instead of .wrappedValue

Trying to call the property as a function

Using array indexing syntax

Use .wrappedValue to access the actual value stored by the property wrapper.

2fill in blank

medium

Complete the code to access the projected value of the property wrapper.

Swift

struct User {
    @Logged var name: String

    func printLog() {
        print($name[1])
    }
}

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

A.projectedValue

B.wrappedValue

C()

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Using .wrappedValue instead of .projectedValue

Forgetting the $ prefix

Trying to call the property as a function

Use .projectedValue to access the extra value or functionality the wrapper provides, accessed via the $ prefix.

3fill in blank

hard

Fix the error in accessing the wrapped value inside the property wrapper struct.

Swift

@propertyWrapper
struct Logged {
    private var value: String

    var [1]: String {
        get { value }
        set { value = newValue }
    }

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

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

AprojectedValue

BwrappedValue

Cvalue

Dwrapped

Attempts:

3 left

💡 Hint

Common Mistakes

Using projectedValue instead of wrappedValue

Using a different property name like value or wrapped

The property wrapper must define a property named wrappedValue to work correctly.

4fill in blank

hard

Fill both blanks to define the projectedValue property that returns a log string.

Swift

@propertyWrapper
struct Logged {
    private var value: String
    private(set) var log: String = ""

    var wrappedValue: String {
        get { value }
        set {
            value = newValue
            log += "Value changed to \(newValue)\n"
        }
    }

    var [1]: String {
        return log
    }
}

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

Alog

BwrappedValue

CprojectedValue

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Naming the property wrappedValue instead of projectedValue

Returning value instead of log

The projectedValue property is named projectedValue and returns the log string.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps property names to their wrapped values if the value is not empty.

Swift

struct User {
    @Logged var firstName: String
    @Logged var lastName: String

    func nonEmptyProperties() -> [String: String] {
        [
            "firstName": $firstName[1],
            "lastName": $lastName[2]
        ].filter { $0.value [3] "" }
    }
}

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

A.wrappedValue

B!=

C==

D.projectedValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using .projectedValue instead of .wrappedValue

Using == instead of != in the filter

Forgetting to access wrappedValue

Use .wrappedValue to get the actual value from the projected property, and filter where value is not equal to empty string.