Re: AKClassHierarchy

[PA <petite.abeille@...>]

On Feb 12, 2006, at 04:27, Gavin Kistner wrote:

> 		obj.super.initialize( obj )

Your problem is right there: 'super' cannot be a straight attribute of 
your object for method dispatch purpose. It needs to be part of your 
object context instead.

Short illustration:

Given a 'class' function with setup a class hierarchy [1]:

function class( aName, aSuper )
        local aSuper = aSuper or require( "LUObject" )
        local aClass = package.loaded[ aName ]

        if aClass == nil then
                aClass = aSuper:new()
                package.loaded[ aName ] = aClass
        end

        return aClass, aSuper
end


Define a 'Rectangle' class:

local self, super = class( "Rectangle" )

        function self:init( aValue  )
                super.init( self, aValue )

                self._value = ( aValue or "?" ):upper()

                print( "Rectangle init" )

                return self
        end

        function self:value()
                return self._value
        end

        function self:testMethod()
                return "Rectangle: " .. self:value() .. ": ".. 
self:class() .. " < " .. self:super()
        end


Define a 'Square' class which extends 'Rectangle':

local self, super = class( "Square", require( "Rectangle" ) )

        function self:init( aValue  )
                super.init( self, aValue )

                print( "Square init" )

                return self
        end

        function self:testMethod()
                return "Square: " .. self:value() .. ": ".. 
self:class() .. " < " .. self:super()
        end


And finally define a 'UnitSquare' class which extends 'Square':

local self, super = class( "UnitSquare", require( "Square" ) )

        function self:init( aValue  )
                super.init( self, aValue )

                print( "UnitSquare init" )

                return self
        end

        function self:testMethod()
                return "UnitSquare: " .. self:value() .. ": ".. 
self:class() .. " < " .. self:super()
        end


'Rectangle', 'Square' and 'UnitSquare' each invoke their parent 'init' 
method.

print( "*", require( "Rectangle" ):new( "hello1" ):testMethod() )
print( "*", require( "Square" ):new( "hello2" ):testMethod() )
print( "*", require( "UnitSquare" ):new( "hello3" ):testMethod() )

> Rectangle init
> *       Rectangle: HELLO1: Rectangle@1154736 < LUObject@1154352
> Rectangle init
> Square init
> *       Square: HELLO2: Square@1155056 < Rectangle@1154736
> Rectangle init
> Square init
> UnitSquare init
> *       UnitSquare: HELLO3: UnitSquare@1155600 < Square@1155056

Cheers

--
PA, Onnay Equitursay
http://alt.textdrive.com/

[1] http://dev.alt.textdrive.com/browser/lu/LUObject.lua