1. Creating your own classes
2. Class inheritance
3. Overriding methods
4. Final classes
5. Copying objects
6. Deinitializers
7. Mutability
8. Classes summary

1. Creating Classes

Classes are similar to structs in that they allow you to create new types with properties and methods, but they have five important differences and I’m going to walk you through each of those differences one at a time.

The first difference between classes and structs is that classes never come with a memberwise initializer. This means if you have properties in your class, you must always create your own initializer.

class Dog {
    var name: String
    var breed: String
    
    init(name: String, breed: String) {
        self.name = name
        self.breed = breed
    }
}

let poppy = Dog(name: "Poppy", breed: "Poodle")
print(poppy)

2. Class Inheritance

The second difference between classes and structs is that you can create a class based on an existing class – it inherits all the properties and methods of the original class, and can add its own on top.

This is called class inheritance or subclassing, the class you inherit from is called the “parent” or “super” class, and the new class is called the “child” class.

class Dog {
    var name: String
    var breed: String

    init(name: String, breed: String) {
        self.name = name
        self.breed = breed
    }
}

class Poodle: Dog {
    init(name: String) {
        super.init(name: name, breed: "Poodle")
    }
}

3. Overriding Methods

class Dog {
    func makeNoise() {
        print("Woof!")
    }
}

class Poodle: Dog {
    override func makeNoise() {
        print("Yip!")
    }
}

print(Poodle().makeNoise())