Lesson 9 — Classes

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1–8 done · 9. Classes ←

What are we learning?

A class is a blueprint for a kind of value that has:

• fields — named pieces of data
• methods — functions that belong to that kind of value

An object (or instance) is one value made from that blueprint.

Smallest useful example

class Dog {
    new {
        name: str;
    }

    fn bark(this) {
        say(this.name, "says woof");
    }
}

d: Dog = Dog { name: "Rex" };
d.bark();

Output

Rex says woof

Line by line

1. class Dog { ... } — define the blueprint named Dog.
2. new { name: str; } — every Dog has a text field called name.
3. fn bark(this) { ... } — a method. this means “the dog we are talking about.”
4. Dog { name: "Rex" } — create one dog whose name is Rex.
5. d.bark(); — run bark on that dog.

Try it

Create a Cat class with a name field and a meow method that prints the name and says meow. Make one cat and call meow.

Predict it

class Point {
    new {
        x: int;
        y: int;
    }

    fn show(this) {
        say(this.x, this.y);
    }
}

p: Point = Point { x: 3, y: 4 };
p.show();

Show answer

3 4

What we are not covering yet

Interfaces, private fields (priv), getters/setters, type methods, and implements are real Echo features. Learn them after you are comfortable with this page: Classes and Interfaces (full).

You finished the Learn path

Next steps:

1. Practice — Change, predict, fix
2. Small exercises
3. Mini projects
4. When you need exact rules: Language Reference
5. When you already know other languages: Language Tour