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-----------------------------------------------------------------------------------
-- Indexable.lua
-- Enrique García ( enrique.garcia.cota [AT] gmail [DOT] com ) - 11 Aug 2010
-- mixin that includes index method (*NOT* an __index metamethod) on instances of middleclass
-----------------------------------------------------------------------------------
--[[ Usage:
require 'middleclass' -- or similar
require 'middleclass-extras.init' -- or 'middleclass-extras'
MyClass = class('MyClass'):include(Indexable)
function MyClass:initialize(a,b,c)
self.a, self.b, self.c = a,b,c
end
function MyClass:index(name) -- attention! index, not __index !
return 'could not find ' .. tostring(name)
end
local x = MyClass:new(1,2,3)
print(x.a) -- 1
print(x.b) -- 2
print(x.c) -- 3
print(x.d) -- 'could not find d'
]]
assert(Object~=nil and class~=nil, 'MiddleClass not detected. Please require it before using Indexable')
local _metamethods = { -- all metamethods except __index
'__add', '__call', '__concat', '__div', '__le', '__lt', '__mod', '__mul', '__pow', '__sub', '__tostring', '__unm'
}
local function _createInstanceDict(theClass)
local classDict = theClass.__classDict
local instanceDict = {}
for _,mmName in ipairs(_metamethods) do
instanceDict[mmName] = function(...) return classDict[mmName](...) end
end
instanceDict.__index = function(instance, name) return classDict[name] or instance:index(name) end
setmetatable(instanceDict, {__index = classDict})
return instanceDict
end
local function _modifyAllocateMethod(theClass)
local instanceDict = _createInstanceDict(theClass)
local classDict = theClass.__classDict
rawset(theClass, '__instanceDict', instanceDict)
-- modify the instance creator so instances use __instanceDict and not __classDict
local oldAllocate = theClass.allocate
function theClass.allocate(theClass, ...)
return setmetatable(oldAllocate(theClass, ...), theClass.__instanceDict)
end
return theClass
end
local function _modifySubclassMethod(theClass)
local prevSubclass = theClass.subclass
theClass.subclass = function(aClass, name, ...)
return _modifyAllocateMethod(prevSubclass(aClass, name, ...))
end
end
Indexable = {}
function Indexable:included(theClass)
if includes(Indexable, theClass) then return end
_modifyAllocateMethod(theClass)
_modifySubclassMethod(theClass)
end