Re: how to make two different function(object?) share a private value?
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: how to make two different function(object?) share a private value?
- From: Axel Kittenberger <axkibe@...>
- Date: Tue, 7 Dec 2010 10:21:02 +0100
A while long I made a function returning two interfaces, the usual for
the object and another special access access.
function createObject()
local t = {}
local sa = {}
local i = i or 5
function t:Foo()
print("foo, i = ", i)
end
function sa:getI()
return i
end
return t, sa
end
So whereever you create it, you get two handels
o, sa = createObject
and pass the normal away and keep the special interface
If you have to get special access from normal object only, you can
make a table for that.
local oToSa = {}
setmetatable(oToSa, __mode = "k")
function createObject()
local t = {}
local sa = {}
local i = i or 5
function t:Foo()
print("foo, i = ", i)
end
function sa:getI()
return i
end
oToSa[o] = sa
return t, sa
end
now whoever has access to oToSa can get the special interface from the object,
setmetatable(oToSa, __mode = "k")
Advices the garbage collector to delete the entry in the table if the
object is no longer used.
On Tue, Dec 7, 2010 at 2:33 AM, starwing <weasley.wx@gmail.com> wrote:
> hi, everyone :-)
> now I made a OO style with lua, use a table of closure:
> function object(i)
> local t = {}
> local i = i or 5
> function t:Foo()
> print("foo, i = ", i)
> end
> return t
> end
> now "i" is a true private data member in class object. only function Foo can
> "see" what i is,
> but, when i use this tech to implement a control-contianer complement
> system, I have to put member data to the table: because I must let Control
> object and Container object all access the member data! in C++, we can do it
> with friend class, but I can not do this in lua:
> function Control(parent)
> local t = {}
> ....
> local has_focus
> function t:SetFocus(focus)...end
> function t:HasFocus() return has_focus end
>
> ...
> return t
> end
> function Container(parent)
> local t = Control(parent) -- Container is-a Control
> local focus_child
> function t:SetFocusChild(child)...end
> function t:GetFocusChild() return focus_child end
> ...
> return t
> end
>
> Control().SetFocus can change the value of "has_focus", but SetFocusChild
> can't do that, it must use something to change the value of has_focus, and
> this thing must not call by user himself. (because these function e.g.
> SetRawFocus can not change "focus_child" value in Container, so it will
> break data), or I could put has_focus to public area(i.e. put it in table),
> but in this scene, anybody can change its value.
> i just want a function SetFocus can change the value of focus_child, and a
> function SetFocusChild can change the value of has_focus. i.e. these two
> closure-variable are shared by two linked object.
> has anybody have good idea to do this?