Re: Inheriting from a userdata object

[Peng Zhicheng <pengzhicheng1986@...>]

于 2012-6-18 17:06, Stephen Virgo 写道:

is that actually sufficient to make 

my_game:out("foo") 

reduce to 

__proto__.out(__proto__,"foo") ?

 

i don't use the ":" sugar much, but, i didn't think it was that sophisticated... shouldn't it just yield

__proto__.out( my_game ,"foo") ?

I think you could be correct, the lua snippet from Peng Zhicheng didn't work with the same "calling 'out' on bad self (game_class expected, got table)" error. I wonder if this is possible..

*account changed to prevent corporate sig spam

sorry about that. the code in my last post is incorrect.
one possible working __index function might be like this:

---------------------------- code begine -------------------------------------
---
-- the __index meta method will do the following:
--   firstly get the indexed field of the wrapped object(i.e. the proto)
--   if the field is not a method(i.e. function), just return it
--   else return a wrapped function to call the method on the wrapped object
-- note however if the field indexed is just retrived but not called on
--   the wrapper object, unwanted behavior might occur.

function game_wrapper_mt:__index(key)
    local proto = rawget(self, "__proto__")
    local field = proto and proto[key]
    if type(field) ~= "function" then
        return field
    else
        return function (obj, ...)
            if obj == self then
                return field(proto, ...)
            else
                return field(obj, ...)
            end
        end
    end
end
----------------------------- code end ---------------------------------------

best regards.