Re: Capturing Lua variable as a string
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- Subject: Re: Capturing Lua variable as a string
- From: Romulo Bahiense <romulo@...>
- Date: 2007年10月01日 08:30:59 -0300
Julien Hamaide wrote:
Lythoner LY wrote:
Hi All,
>> (snip)
if you have a limited number of type, you can define them as global
variable :
INT = "INT"
FLOAT = "FLOAT"
function DEF_PARAM(v)
-- do something here to set NAME property from v
-- v["NAME"] = ???? How do I get string equivalent of variable v
return v
end
Just load this script before your definition file, and TYPE will
automatically contain the text.
I think he meant the name of the variable:
>> In shell,
>>
>>> print(DeviceParam3.NAME)
>> DeviceParam3
>>
>>> print (type(DeviceParam3.NAME)
>> string
Unfortunately, it is not possible to know what is the name of the
variable you are assigning to (inside the DEF_PARAM function, of
course). What I suggest, is to __newindex the chunk's environment and
post-assign the name. Something like:
myconfiguration.lua:
DeviceParam1 = DEF_PARAM{ TYPE = INT }
DeviceParam2 = DEF_PARAM{ TYPE = INT }
DeviceParam3 = DEF_PARAM{ TYPE = INT }
~~ end of myconfiguration.lua:
configloader.lua
function load( filename )
local f = assert( loadfile( filename ) )
local e = setmetatable( {}, {
__index = _G;
__newindex = function( t, k, v )
if type( k ) == 'string' and type( v ) == 'table' then
v.NAME = k
end
end; } )
setfenv( f, e )
f()
end
~~ end of configloader.lua
Of course, this will cause all assignments of tables to global variables
be changed. You can make some tricks to only assign the NAME fields to
a particular subset. First, you can check for the presence of a TYPE
attribute as a pre-condition (trivial). Second, you can store the newly
created table in another table while creating it with DEF_PARAM and then
check if the table being assigned belongs to it:
configloader2.lua
function load( filename )
local f = assert( loadfile( filename ) )
local t = {}
local old_DEF_PARAM = DEF_PARAM
local e = setmetatable(
{
DEF_PARAM = function( info )
-- In case DEF_PARAM creates another table...
info = old_DEF_PARAM( info )
t[ info ] = true
return info
end;
}, {
__index = _G;
__newindex = function( t, k, v )
if t[ v ] then
v.NAME = k
end
end;
}
)
setfenv( f, e )
f()
end
~~ end of configloader2.lua
Hope that helps,
--rb