getset.lua

A library for defining getters and setters on Lua tables by Josh Tynjala.

Usage

local getset = require("getset")

function createSimple2DPoint()
	local _x = 0
	local _y = 0
	local point = {}
	getset.defineProperty( point, "x",
	{
		get = function()
			return _x
		end,
		set = function( value )
			_x = value
		end
	})
	getset.defineProperty( point, "y",
	{
		get = function()
			return _y
		end,
		set = function( value )
			_y = value
		end
	})
	
	getset.defineProperty(point, "length",
	{
		get = function()
			return math.sqrt(_x * _x + _y * _y)
		end
		-- no setter required
	})
	
	-- prevents new fields from being added later, and existing fields cannot
	-- be configured (we can't redefine the getters and setters later).
	-- see also: getset.preventExtensions()
	return getset.seal(point)
end

local myPoint = createSimple2DPoint()
myPoint.x = 4
myPoint.y = 4

-- returns 5.6568542494924:
local myPointLength = myPoint.length

-- runtime error because the table is not extensible:
myPoint.z = 7 

-- runtime error because length has no setter:
myPoint.length = 9 

-- runtime error because table is sealed:
getset.defineProperty( myPoint, "x",
{
	get = function()
		return 1
	end
})

API

The getset library offers the following functions. For more detailed descriptions, see the documentation above each function in getset.lua.

getset.defineProperty( table, key, descriptor )

Defines a getter and a setter on a table for a specific key. Both are optional.

getset.preventExtensions( table )

Prevents new properties from being added to a table. Existing properties may be modified and configured.

getset.isExtensible( table )

Determines if a table is may be extended.

getset.seal( table )

Prevents new properties from being added to a table, and existing properties may be modified, but not configured.

getset.isSealed( table )

Determines if a table is sealed.