Use of final keyword in method and class

Uplift iOS Interview

The Guide is for YOU if

• You are preparing for an iOS interview and want to improve your skills and knowledge and looking to level up your interview game and land your dream job.
• You want to gain confidence and ease during iOS interviews by learning expert tips and curated strategies.
• You want access to a comprehensive list of iOS interview QA to practice and prepare.

I want this

The Final is a class modifier that prevents it from being inherited or being overridden. While writing an API developer might have a class in the framework that can be abused or misused when subclassed. The solution will be the “final” keyword in this case which prevents class to be subclassed. You can also use final to methods, properties, and even subscripts of non-final classes. This will have the same effect, but for a particular part of the class.

For class declaration by default, I am using the final keyword. When we use final keyword declaration, it does not need to be overridden which has better performance because final disables dynamic dispatch at runtime(saves runtime overhead).

KEY TAKEWAYS

Final is used to prevent a class from being subclassed or a method from being overridden.

// Final is used to prevent a class from being subclassed 
// or a method from being overridden.
class GrumpyCat {
    func eat() {
        // nom nom
    }

    func sleep() {
       // Zzz Zzz
    }

    // Preventing overrides by final keyword
    final func play() {
        // GrumpyCat don't want to play
    }
}

class FatGrumpyCat: GrumpyCat {
    // This can be easily overridden 
    override func eat() {
        super.eat()
        // Want to eat more
    }
}

final class HappyCat {
    func chill() {
        // HappyCat will play
    }
}

//ERROR:inheritance from a final class 'HappyCat' class Cat
class Cat: HappyCat {
    override init() {
    }
}

Written by

ISHTIAK AHMED

Twitter LinkedIn

Get Ready to Shine: Mastering the iOS Interview

• Uplift iOS Interview - A Comprehensive Guide to iOS Interview
• iOS Dev Kit - Cheat Sheets, Posters and Infographics

Enjoying the articles? Get the inside scoop by subscribing to my newsletter.

Get access to exclusive iOS development tips, tricks, and insights when you subscribe to my newsletter. You'll also receive links to new articles, app development ideas, and an interview preparation mini book. Your email address will only be used for the purpose of sending the newsletter and will not be shared with third parties or advertisers. Rest assured that we value your privacy and will not spam your inbox.