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Shouldn't the Text View be using the Model, instead of caching the strings?

Are the View & Model made in C(++) or in Lua?


On Fri, 1 Dec 2006 15:24:51 +0800
 "wang xu" <xu4wang@gmail.com> wrote:

Hi Rici,

Thanks for the reply!

See my comments below.


2006/12/1, Rici Lake <lua@ricilake.net>: 


On 1-Dec-06, at 12:31 AM, wang xu wrote:

> Is there a generic way to automatically update one variable when the
> value of another variable is changed?

No. (And why do you want to do that?)



I have a View, the view is a Text Widget, which has an attribute "str", when
the str is modified, the Text widget will update the Screen with the string.

I also have a Model, which is a table containing many strings, each string
is corresponding to one Text Widget.

What I want to do by a linked variable are:
1) when a string in the model changes, the str in the view update
automatically.
2) when the str in the Text Widget changes(by the user through GUI), the
sting in the Model table update automatically too.

The closest you can do is to implement your own "boxed" values, using 
tables with a single key (say, 1):

val1 = {"a"}
val2 = val1
val1[1] = "b"
=val2[1]

You could dress it up in O-O notation:

do
   local meta = {}
   meta.__index = meta
   function meta:set(v) self[1] = v end
   function meta:get() return self[1] end

   function Box(v)
     return setmetatable({v}, meta)
   end
end

val1 = Box("a")
val2 = val1
=val2:get()
val1:set("b")
=val2:get()


Yeah. that's a way. but I need to change my model and widget
implementation...

I came from the TCL world, and there is a tracevar can do this, so I'm
wondering if Lua has similar functionality..