Use of final keyword in method and class

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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).


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() {
        // 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() {

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