Classes and methods

Records model transparent values. A class instead creates objects with identity and can keep mutable state behind methods.

public class Counter
    private value: Int = 0

    public function Counter:increment()
        self.value = self.value + 1
    end

    public function Counter:current(): Int
        return self.value
    end
end

Inside an instance method, the class name before : declares the receiver type, and self refers to the receiving object. The private field can be read and assigned by the class’s own methods.

Constructing an object

A class construction names the class and supplies its fields. Fields with compile-time defaults may be omitted:

local counter = Counter {}

Call an instance method with a colon:

counter:increment()
print(counter:current())

The colon makes the receiver explicit: counter is the object on which the method operates. Dot syntax is used for fields and for functions associated with a type rather than an object.

Identity

Class values refer to managed objects. Assigning one to another local does not copy its fields:

local first = Counter {}
local second = first
second:increment()
print(first:current()) -- 1

first and second refer to the same object. Class equality compares this identity, not a field-by-field snapshot.

Encapsulation

Fields and methods may be public, internal, or private. Private state lets a class maintain rules that callers cannot bypass. A method can validate an operation before changing a field, while callers work through a stable public interface.

Classes in this release are nominal: their declared identity matters even when another class happens to contain the same fields. General source-level inheritance is not part of the supported 0.1.0-rc.2 feature set. Use interfaces to describe shared behavior.