Preventing overrides with final in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to prevent the method from being overridden.

Swift

class Vehicle {
    [1] func startEngine() {
        print("Engine started")
    }
}

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

Aopen

Boverride

Cfinal

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'override' instead of 'final'.

Using 'open' which allows overriding.

Forgetting to add any keyword.

Using 'final' before a method prevents subclasses from overriding it.

2fill in blank

medium

Complete the code to prevent the class from being subclassed.

Swift

[1] class Animal {
    func sound() {
        print("Some sound")
    }
}

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

Afinal

Bopen

Cpublic

Doverride

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'open' which allows subclassing.

Using 'override' which is for methods, not classes.

Not adding any keyword.

Marking a class as 'final' stops other classes from inheriting it.

3fill in blank

hard

Fix the error in the subclass trying to override a final method.

Swift

class Car {
    final func drive() {
        print("Driving")
    }
}

class SportsCar: Car {
    [1] func drive() {
        print("Fast driving")
    }
}

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

Aopen

Boverride

Cpublic

Dfinal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'override' keyword on a final method.

Trying to change access level with 'public' or 'open'.

You cannot override a final method; removing 'override' or marking method as 'final' in subclass is needed.

4fill in blank

hard

Fill both blanks to prevent subclassing and method overriding.

Swift

[1] class Bird {
    [2] func fly() {
        print("Flying")
    }
}

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

Afinal

Bopen

Cpublic

Doverride

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'open' which allows subclassing and overriding.

Mixing 'public' and 'override' keywords incorrectly.

Marking both the class and method as 'final' stops subclassing and overriding.

5fill in blank

hard

Fill all three blanks to create a final class with a final method and a non-final method.

Swift

[1] class Plane {
    [2] func takeOff() {
        print("Taking off")
    }
    [3] func land() {
        print("Landing")
    }
}

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

Afinal

Bopen

Coverride

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Marking the class as 'open' which allows subclassing.

Using 'override' keyword incorrectly on methods.

Not marking the method as 'final' to prevent overriding.

The class and takeOff method are final to prevent subclassing and overriding; land method is public and can be overridden if subclassing was allowed.