Augmentations

implements

impl statement allows the developer to augment the given class or namespace.

syntax

impl varname {
(field | method)*
}

field = varname[: type] [= value]

method = [async] varname([[parameter1] [, [parameter2] ... [, [parameterN]]])[: type] [~ class1 [, class2 ... [, classN]]] [ => expression | {
...statements
}]

example

impl Shape {
	draw(shape): String {
		return `I'm drawing a \(@color) \(shape).`
	}
}
// adds the method 'draw(shape)' to the class 'Shape'

let s = new Shape('red')

console.log(s.draw())
// I'm drawing with a red pen

console.log(s.draw('circle'))
// I'm drawing a red circle.

implements & native class

impl doesn't modify classes that have been flagged as sealed.

extern sealed class Number
// import the external class 'Number' and flag it as `sealed` to avoid to directly modify it

impl Number {
	mod(max: Number): Number {
		if this == NaN {
			return 0
		}
		else {
			const n = this % max

			if n < 0 {
				return n + max
			}
			else {
				return n
			}
		}
	}
}
// adds the method 'mod' to the class 'Number'
// under the hood, the object `__ks_Number` is created to avoid to modify the object 'Number'

let i = 42
// inferred type: Number

console.log(i.mod(2))
// 0
// javascript code: console.log(__ks_Number._im_mod(i, 2))

override

The modifier override indicate that the new method will replace the existing one.

class LetterBox {
	format(message: String) => message.toUpperCase()
}

impl LetterBox {
	override format(message: String) => message.toLowerCase()
}