Lua Interface

wiki

Web sites:

• http://code.google.com/p/luainterface (latest 2.x source code / issues)
  • [version 1.5.4 beta???]
• http://www.lua.inf.puc-rio.br/luanet/luainterface/ (PUC description page)
• http://luaforge.net/projects/luainterface/ (old project page)
• http://luaforge.net/forum/?group_id=50 (mailing lists)
• [LuaInterface Tutorial] (version 1.5.3, on penlight/luaforwindows page)
• [LuaInterface: Scripting the .NET CLR with Lua] (2004 paper)
• [luainterface-debugger] - debugger extension for LuaInterface
• Lua2IR (link broken in [1]) and as noted here LuaList:2007-10/msg00544.html apparently replaced by [LuaCLR].

Dependencies: .NET. Also works on the Mono runtime http://www.mono-project.com on Linux.

Note: Version 1.5.3 builds a C module DLL that can loaded in regular Lua interpreter. Version 2.0 and above are completely managed code. [4][5][6][7][2][3]

User Comments

Not mentioned in the LuaInterface documentation is how to instantiate .NET arrays. It is done simply by indexing a type reference with a number:

local a = SomeType[5]

for i = 1,a.Length do

	print(i, a[i - 1]) -- .NET arrays are zero-based.

end

When using the CLR from Lua, the ordinary method of loading types and classes can seem a little verbose:

net = require "luainterface"



net.load_assembly("System.Windows.Forms")

net.load_assembly("System.Drawing")



Form = net.import_type("System.Windows.Forms.Form")

Button = net.import_type("System.Windows.Forms.Button")

Point = net.import_type("System.Drawing.Point")



local form1 = Form()

local button1 = Button()

button1.Location = Point(10, 10)

It would be nice if syntax like this could be used:

require "net"



Form = net.System.Windows.Forms.Form

Button = net.System.Windows.Forms.Button

Point = net.System.Drawing.Point



local form1 = Form()

local button1 = Button()

button1.Location = Point(10, 10)

Optionally, the .NET types can be made to appear as toplevel names:

require "net"



System = net.System



Form = System.Windows.Forms.Form

Button = System.Windows.Forms.Button

Point = System.Drawing.Point



local form1 = Form()

local button1 = Button()

button1.Location = Point(10, 10)

It should not be necessary to make every type name toplevel:

require "net"



System = net.System



local form1 = System.Windows.Forms.Form()

local button1 = System.Windows.Forms.Button()

button1.Location = System.Drawing.Point(10, 10)

Here is the method:

-- Create a metatable for our name components

local metatable = { [".NET"] = {getmetatable=getmetatable} }



-- Load LuaInterface

local g = getfenv(0)

setfenv(0, metatable[".NET"])

local init, e1, e2 = loadlib("LuaInterfaceLoader.dll", "luaopen_luainterface")

assert(init, (e1 or '') .. (e2 or ''))

init()

setfenv(0, g)



-- Lookup a .NET identifier component.

function metatable:__index(key) -- key is e.g. "Form"

    local mt = getmetatable(self)

    local luanet = mt[".NET"]



    -- Get the fully-qualified name, e.g. "System.Windows.Forms.Form"

    local fqn = ((self[".fqn"] and self[".fqn"] .. ".") or "") .. key



    -- Try to find either a luanet function or a CLR type

    local obj = luanet[key] or luanet.import_type(fqn)



    -- If key is neither a luanet function or a CLR type, then it is simply

    -- an identifier component.

    if obj == nil then

		-- It might be an assembly, so we load it too.

        luanet.load_assembly(fqn)

        obj = { [".fqn"] = fqn }

        setmetatable(obj, mt)

    end



    -- Cache this lookup

    self[key] = obj

    return obj

end



-- A non-type has been called; e.g. foo = System.Foo()

function metatable:__call(...)

    error("No such type: " .. self[".fqn"], 2)

end



-- This is the root of the .NET namespace

net = { [".fqn"] = false }

setmetatable(net, metatable)



-- Preload the mscorlib assembly

net.load_assembly("mscorlib")



return nil

See Also

• LuaCom
• BindingCodeToLua (.NET)