Inheritance (Extending a Class)

In this lesson you will learn how to extend a class through inheritance in Swift, so classes that share characteristics can reuse code. This is for anyone searching for "Swift inheritance how to use".

You inherit with class Child: Parent, and override replaces a method from the parent. Gathering the shared parts into a parent class saves you writing the same code repeatedly.

The sample code makes Animal the parent, has Dog inherit from it with : Animal, and replaces the parent's method with override func speak(). The key point is that you keep the parent's functionality and change only the parts you need.

A common stumbling block for beginners is forgetting override. Writing a method with the same name as the parent's without it is a compile error - you have to state explicitly that the override is deliberate.

In real-world development, the final keyword is also widely used to stop a class or method from being inherited or overridden any further.

📖 Reference code

class Animal {
    var name: String
    init(name: String) { self.name = name }
    func speak() -> String { return "\(name) makes a sound" }
}

class Dog: Animal {
    override func speak() -> String {
        return "\(name) says \"Woof\""
    }
}

let dog = Dog(name: "Rex")
print(dog.speak())

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🧪 This site can't compile or run Swift directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).