Re: Object system

[Raffaele Salmaso <raffaele@...>]

John Paquin wrote:
> with your class system, is it possible to change the lua code (lass.lua 
> in this case), reload the lua file and expect to see the changes 
> reflected in existing objects (like c in this case)?
No, this version will not work.

> I think that the only way to incorporate dynamic changes is to 
> dynamically (i.e. at the time of reference) follow the inheritance chain 
> backward to find the correct method.
You should use the non-caching version

---8<---
-- this version doesn't cache anything
-- beware that it is slower than the caching one
function class(super)
    -- create a new class description
    local klass = {}
    -- set the superclass (for object inheritance)
    setmetatable(klass, {
        __index = super,
        __call = function(self, ...)
            local tmp = {}
            setmetatable(tmp, klass)
            if self.init then
                self.init(tmp, unpack(arg))
            end
            return tmp
        end
    })
    klass.__index = function(table, key)
        local r = klass[key]
        if type(r) == 'function' then
            return function(...) return r(table, unpack(arg)) end
        else
            return r
        end
    end
    return klass
end

object = class()
function object.__tostring(self)
    return 'first version'
end

print(c)

function object.__tostring(self)
    return 'second version'
end

print(c)
--->8---

this will print:
first version
second version

If you use the other version, you will get[1]:
first version
first version

The drawback is that is is slow, more slower than caching version.
See the other mails in this thread for some timing.

[1] in reality its all depend only when you call the method for the 
first time: the first time you will freeze it.

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