Classes

Classes in Zeus provide a way to create custom types with properties and methods.

Basic Class

class Rectangle {
  public width: f64;
  public height: f64;
}

function main(): i32 {
  let rect: Rectangle = new Rectangle();
  rect.width = 10.0;
  rect.height = 5.0;

  return 0;
}

Constructors

Use constructor to initialize objects:

class Point {
  public x: i32;
  public y: i32;

  constructor(x: i32, y: i32) {
    this.x = x;
    this.y = y;
  }
}

function main(): i32 {
  let p: Point = new Point(10, 20);
  return p.x + p.y;  // Returns 30
}

Methods

Classes can have methods that operate on the object:

class Rectangle {
  public width: f64;
  public height: f64;

  constructor(w: f64, h: f64) {
    this.width = w;
    this.height = h;
  }

  public area(): f64 {
    return this.width * this.height;
  }

  public perimeter(): f64 {
    return 2.0 * (this.width + this.height);
  }
}

function main(): i32 {
  let rect: Rectangle = new Rectangle(10.0, 5.0);
  let a: f64 = rect.area();       // 50.0
  let p: f64 = rect.perimeter();  // 30.0

  return 0;
}

The `this` Keyword

Inside a class, this refers to the current instance:

class Counter {
  public value: i32;

  constructor(start: i32) {
    this.value = start;
  }

  public increment(): void {
    this.value = this.value + 1;
  }

  public add(amount: i32): void {
    this.value = this.value + amount;
  }

  public getValue(): i32 {
    return this.value;
  }
}

Access Modifiers

Zeus supports public and private access modifiers:

class BankAccount {
  private balance: i32;
  public accountId: i32;

  constructor(id: i32, initialBalance: i32) {
    this.accountId = id;
    this.balance = initialBalance;
  }

  public deposit(amount: i32): void {
    this.balance = this.balance + amount;
  }

  public getBalance(): i32 {
    return this.balance;
  }
}

function main(): i32 {
  let account: BankAccount = new BankAccount(1, 100);
  account.deposit(50);

  // account.balance = 0;  // Error: 'balance' is private

  return account.getBalance();  // 150
}

Nested Objects

Classes can contain other objects as properties:

class Point {
  public x: i32;
  public y: i32;

  constructor(x: i32, y: i32) {
    this.x = x;
    this.y = y;
  }
}

class Line {
  public start: Point;
  public end: Point;

  constructor(p1: Point, p2: Point) {
    this.start = p1;
    this.end = p2;
  }

  public length(): i32 {
    let dx: i32 = this.end.x - this.start.x;
    let dy: i32 = this.end.y - this.start.y;
    return dx + dy;  // Simplified (Manhattan distance)
  }
}

function main(): i32 {
  let p1: Point = new Point(0, 0);
  let p2: Point = new Point(10, 20);
  let line: Line = new Line(p1, p2);

  return line.length();  // Returns 30
}

Object References

Objects are passed by reference:

class Box {
  public value: i32;

  constructor(v: i32) {
    this.value = v;
  }
}

function modifyBox(box: Box): void {
  box.value = 999;
}

function main(): i32 {
  let myBox: Box = new Box(10);
  modifyBox(myBox);

  return myBox.value;  // Returns 999
}

Null Objects

Object variables can be null:

class Node {
  public value: i32;
  public next: Node;

  constructor(v: i32) {
    this.value = v;
    this.next = null;  // No next node
  }
}

function main(): i32 {
  let node: Node = new Node(42);
  // node.next is null

  return node.value;
}

Method Chaining

Methods can return this for chaining (when returning the same type):

class Builder {
  public x: i32;
  public y: i32;
  public z: i32;

  constructor() {
    this.x = 0;
    this.y = 0;
    this.z = 0;
  }

  public setX(val: i32): i32 {
    this.x = val;
    return this.x;
  }

  public setY(val: i32): i32 {
    this.y = val;
    return this.y;
  }
}

Classes with Arrays

Classes can have array properties:

class Team {
  public scores: i32[];

  constructor() {
    this.scores = new i32[];
  }

  public addScore(score: i32): void {
    this.scores.push(score);
  }

  public getScore(index: i32): i32 {
    return this.scores.get(index);
  }
}

function main(): i32 {
  let team: Team = new Team();
  team.addScore(10);
  team.addScore(20);
  team.addScore(30);

  return team.getScore(1);  // Returns 20
}

Arrays →