Classes and Instances

Create a class by passing a definition table to Class.

local Class = require("class")

local Counter = Class({
	__type = "Counter",

	init = function(self, value)
		self.value = value or 0
	end,

	increment = function(self)
		self.value = self.value + 1
		return self.value
	end,
})

local counter = Counter(10)
counter:increment()

Initialization

init is called automatically when an instance is created.

local user = User("Ada")

Arguments passed to the class call are forwarded to init.

Type names

Set __type when you want readable debug output and clearer error messages.

local User = Class({
	__type = "User",
})

If omitted, the default type is "Class".

Type identity

Each instance stores its class in __class. Prefer class-table checks when you need reliable validation.

local user = User()

print(user.__class == User)
print(Class:is(user, User))
print(user:Is(User))

Class:is(value, expected) returns true when value is an instance of expected, or when its class includes expected as a parent.

Class:assertIs(user, User, "user")
user:AssertIs(User, "user")

__type string checks are supported for convenience, but they are less strict than checking against the class table itself.

Positional init shorthand

The first item in the definition table can be used as init.

local Point = Class({
	function(self, x, y)
		self.x = x
		self.y = y
	end,
})