Lykn

Getters and Setters

Accessor properties look like data but run code when accessed or assigned.

(class Rectangle ()
  (constructor (width height)
    (assign this:width width)
    (assign this:height height))

  (get area ()
    (return (* this:width this:height))))

(bind r (new Rectangle 10 5))
(console:log r:area)           ;; → 50

class Rectangle {
  constructor(width, height) {
    this.width = width;
    this.height = height;
  }
  get area() {
    return this.width * this.height;
  }
}
const r = new Rectangle(10, 5);
console.log(r.area);           // → 50

r:area looks like a property access — no parentheses, no arguments. But area is a getter that runs a computation every time it’s read. The colon syntax works identically for data properties and accessor properties; the difference is invisible at the call site.

Setters work the same way, using set instead of get in the class definition. Both appear primarily in class bodies (kernel passthrough territory). Their full treatment comes in Chapter 20 (Classes).