Defining a Class in Swift in Swift

Full lesson:

So far, you've worked with built-in types like Int, String, and arrays. But what if you want to model something the language doesn't have a type for — like a Dog, a BankAccount, or a Game?

That's what classes are for. A class lets you define your own type by listing what data it holds and what actions it can perform.

Why classes?

Imagine you're writing a program about dogs. Each dog has a name, an age, and can bark. Without classes, you'd have to track each dog's name in one variable, age in another, and write a separate bark() function for each. That gets messy fast.

With a class, you bundle all of that into one neat package called Dog:

class Dog {
    // We'll add fields (data) and methods (behavior) here in upcoming lessons.
}

The syntax

Defining an empty class in Swift looks like this:

class ClassName {
}

Three things to notice:

• The keyword class tells Swift you're defining a new type.

• ClassName is the name you choose. By convention, Swift class names use PascalCase — capitalized words with no underscores: Dog, BankAccount, HighScore.

• The curly braces { } hold the body of the class. They can be empty for now.

Your task

Define an empty class called Dog. The pre-filled code in mainFunction will create an instance of your class and print a confirmation message. If you define the class correctly, the program will compile and print:

Defined the Dog class!