Unowned references for guaranteed lifetime in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an unowned reference to avoid retain cycles.

Swift

class Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Apartment {
    unowned var tenant: [1]
    init(tenant: Person) {
        self.tenant = tenant
    }
}

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AString

BApartment

CInt

DPerson

Attempts:

3 left

💡 Hint

Common Mistakes

Using a value type like String or Int for unowned reference.

Using the wrong class name for the unowned property.

The unowned reference must be of the class type it refers to, here Person.

2fill in blank

medium

Complete the code to declare an unowned reference correctly.

Swift

class Customer {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class CreditCard {
    unowned [1] customer: Customer
    init(customer: Customer) {
        self.customer = customer
    }
}

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Avar

Bunowned

Clet

Dweak

Attempts:

3 left

💡 Hint

Common Mistakes

Using var instead of let for unowned reference.

Confusing weak and unowned references.

An unowned reference must be declared with let because it cannot be nil after initialization.

3fill in blank

hard

Fix the error in the code by choosing the correct keyword for the reference to avoid a runtime crash.

Swift

class Owner {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class House {
    [1] var owner: Owner?
    init(owner: Owner) {
        self.owner = owner
    }
}

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Aweak

Blazy

Cunowned

Dstrong

Attempts:

3 left

💡 Hint

Common Mistakes

Using unowned for optional references that can become nil.

Using strong reference causing retain cycles.

Since owner is optional and can become nil, it should be a weak reference to avoid crashes.

4fill in blank

hard

Fill both blanks to create a class with an unowned reference and initialize it properly.

Swift

class Driver {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Car {
    [1] var driver: Driver
    init(driver: [2]) {
        self.driver = driver
    }
}

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Aunowned

Bweak

CDriver

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using weak instead of unowned for guaranteed lifetime.

Using wrong type for the parameter.

The driver property is an unowned reference of type Driver.

5fill in blank

hard

Fill all three blanks to create a pair of classes with unowned references to avoid retain cycles.

Swift

class Teacher {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Classroom {
    [1] var teacher: Teacher
    init(teacher: [2]) {
        self.teacher = teacher
    }
    func assignTeacher() -> [3] {
        return teacher.name
    }
}

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Aunowned

BTeacher

CString

Dweak

Attempts:

3 left

💡 Hint

Common Mistakes

Using weak instead of unowned for guaranteed lifetime.

Returning wrong type from the function.

The teacher property is an unowned reference of type Teacher, and the function returns a String.