Re: Cleaning up specific lua scripts

[Pierre-Yves Gérardy <pygy79@...>]

I'm glad I could help :-)
You could add a collectgarbage() call at the end of cleanLevel().

That said, the setfenv() solution is probably more elegant and more robust.




local protectMT = {__newindex=error}
local levelMT = {index=_G}

local MTindex

local function protectTable(tbl,index)
    for k,v in pairs(tbl) do
        if
            type(v)==table and
            getmetatable(v) ~= protectMT -- prevents from getting lost in
        then                             -- circular references.
            index[k]={getmetatable(v),{})
            protectTable(v,index[k][2])
            setmetatable(v,protectMT)
        end
    end
end

local function unprotectTable(tbl,index)
    for k,v in pairs(tbl) do
         if type(v)=="table" then
              setmetatable(v,index[k][1])
              unprotectTable(v,index[k][2])
        end
    end
end


local loadLevel = function(levelpath)
    local levelenv=setmetatable({},levelMT)
    local levelcode=loadfile(levelpath)
    setfenv(levelcode,levelenv)
    protectTable(_G,MTindex)
    -- it's now impossible to add or modify any global, or any
subtable of a global.
    local ret = levelcode()
    unprotectTable(_G,MTindex)
    return ret
end

To give back the control from a level, return from it's main chunk
(e.g., return true on level completion and false on death).

local success = loadlevel(level1)
collectgarbage()

if success then
    loadNextLevel()
else
    restartLevel()
end

The above code is not tested and may contain syntax or semantic
errors, but you get the idea :-)

Cheers,
-- Pierre-Yves



On Thu, Mar 25, 2010 at 09:14, Ricky Haggett <ricky@honeyslug.com> wrote:
> Pierre,
>
> This is a simpler and more elegant version of what I implemented yesterday afternoon, which also seemed to do the job, albeit with more fuss..  I'm definitely going to upgrade to your code today..
>
> Thanks,
>
> Ricky
>
> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Pierre-Yves Gérardy
> Sent: 24 March 2010 19:27
> To: Lua list
> Subject: Re: Cleaning up specific lua scripts
>
> On Wed, Mar 24, 2010 at 12:30, Ricky Haggett <ricky@honeyslug.com> wrote:
>> Yep, we could store a table of all of the functions / tables within a
>> specific level script, but it would be awkward for the designers to
>> maintain, and a potential source of error...
>
> You could also do it the other way around:
> after you've loaded your global scripts do
>
> globals={}
>
> function cleanLevel()
>    for k,_ in pairs(_G) do
>        if not globals[k] then _G[k] = nil
>    end
> end
>
> for k,_ in pairs(_G) do
>    globals[k]=true
> end
>
> globals will index all globals present at that point (including itself
> and cleanlevel() ), and cleanLevel() will only delete the globals not
> referenced there. Case solved :-)
>
> Cheers,
> -- Pierre-Yves
>
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