Re: Wrapping "Classes" seamlessly

[PA <petite.abeille@...>]

On May 15, 2006, at 20:33, jdarling@eonclash.com wrote:

> Also does anyone know how hard it is to overload/override the default
> require's handler?  I'd like to be able to redirect require and
> dofile when editing the scripts so that if a modified version exists
> in memory it is used over the one on disk.

Assuming you are keeping track of your "edited" file, this should be 
pretty trivial as far as 'require' goes:

package.loaded[ aModuleName ] = loadstring( aModuleSource )()

Doing the opposite -e.g. reloading a module if its source has changed 
on disk- is a bit more convoluted as you need to figure out where the 
module was loaded from and keep track of its time stamp.

Here is a tortuous and probably boggy example, using LuaFileSystem [1] 
to access a package modification date:

----8<----

require( "lfs" )

local _require = require
local _packages = {}

require = function( aName )
        local aModule = _require( aName )
        local aPackage = _packages[ aName ]

        if type( aModule ) ~= "table" then
                aModule = _G[ aName ]
        end

        if aPackage == nil and type( aModule ) == "table" then
                for aKey, aValue in pairs( aModule ) do
                        if type( aValue ) == "function" then
                                local someInfo = debug.getinfo( aValue, 
"S" )
                                local aSource = someInfo.source

                                if aSource ~= nil and aSource:byte() == 
64 then
                                        aPackage = {}
                                        aPackage.source = aSource:sub( 
2 )
                                        aPackage.time = lfs.attributes( 
aPackage.source, "modification" )

                                        _packages[ aName ] = aPackage

                                        break
                                end
                        end
                end
        end

        if aPackage ~= nil then
                local aTime = lfs.attributes( aPackage.source, 
"modification" )

                if aTime > aPackage.time then
                        aPackage.time = aTime
                        package.loaded[ aName ] = nil

                        return require( aName )
                end
        end

        return aModule
end

----8<----


Cheers

--
PA, Onnay Equitursay
http://alt.textdrive.com/


[1] http://www.keplerproject.org/luafilesystem/