Why inheritance is class-only in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class that inherits from another class.

Swift

class Dog: [1] {
    func bark() {
        print("Woof!")
    }
}

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

Aenum

Bstruct

Cprotocol

DAnimal

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to inherit from a struct or protocol.

In Swift, a class inherits from another class by specifying the parent class name after a colon.

2fill in blank

medium

Complete the code to override a method in a subclass.

Swift

class Animal {
    func sound() {
        print("Some sound")
    }
}

class Cat: Animal {
    override func [1]() {
        print("Meow")
    }
}

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

Abark

Bmeow

Csound

Dnoise

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name that does not exist in the parent class.

The subclass overrides the method from the parent class by using the same method name.

3fill in blank

hard

Fix the error in the code by choosing the correct type that supports inheritance.

Swift

[1] Vehicle {
    var wheels: Int
    init(wheels: Int) {
        self.wheels = wheels
    }
}

class Car: Vehicle {
    var brand: String
    init(brand: String, wheels: Int) {
        self.brand = brand
        super.init(wheels: wheels)
    }
}

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

Aclass

Bstruct

CVehicle

Dprotocol

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to inherit from a struct or protocol.

Only classes can be inherited from in Swift. Structs cannot be used as a superclass.

4fill in blank

hard

Fill both blanks to create a subclass that calls the superclass initializer.

Swift

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

class Student: [1] {
    var id: Int
    init(name: String, id: Int) {
        self.id = id
        [2].init(name: name)
    }
}

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APerson

Bsuper

Cstruct

Dself

Attempts:

3 left

💡 Hint

Common Mistakes

Using self.init instead of super.init to call the superclass initializer.

The subclass Student inherits from Person and calls the superclass initializer using super.init.

5fill in blank

hard

Fill all three blanks to define a class-only protocol and a class that conforms to it.

Swift

protocol [1]: [2] {
    func play()
}

class Guitarist: [3] {
    func play() {
        print("Playing guitar")
    }
}

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APlayable

BAnyObject

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to restrict protocols to structs or enums.

Protocols can be restricted to classes by inheriting from AnyObject. The class then conforms to the protocol.