Lua-Scriptable Type

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Cower	Created : 29 November 2009 Edited : 29 November 2009 Language : Blitz Max Lua-Scriptable Type Small type that allows for easily associating Lua functions to objects
This is sort of a rudimentary example of using LuGI to bind functions to objects in Lua. It could be expanded upon (e.g., binding closures for different messages and such), but it works well enough for the sake of example. Speaking of examples, here's some code and a script to accompany it: woop.bmx Import LuGI.Core Import "scriptable.bmx" Local st@Ptr = luaL_newstate() luaopen_base(st) InitLuGI(st) If luaL_dofile(st, "woop.lua") Then RuntimeError("Error in woop.lua: "+lua_tostring(st, -1)) EndIf Local sc:Scriptable = New Scriptable.Init(st) lua_getglobal(st, "main") lua_pushbmaxobject(st, sc) If lua_pcall(st, 1, 0, 0) Then RuntimeError("Error running woop.lua:main(...): "+lua_tostring(st, -1)) EndIf sc.Activate sc.Dispose ' Disposal is sort of important here since we're holding a reference to something in ' Lua that will be disposed of when the object is deleted. If the object is deleted ' after the Lua state is closed, then you'll have a pretty interesting error. lua_close(st) --v woop.lua function main(obj) --[[ This reduces the amount of questions I have to answer by 50% usually. Although glue code is not necessary for this example, it tends to be when people start hacking on things, and that's when I get the frustrated e-mails because someone forgot to generate the glue code... ]] assert(({pcall(function() return obj.Activate end)})[1], "Error when trying to access Scriptable:Activate (glue code may not be generated)") obj:SetScript( function (self) print(self:ToString()..": Congratulations, you've successfully shattered minds everywhere") end ) end --v scriptable.bmx ?Debug Import LuGI.Generator ? Import LuGI.Core Include "scriptable_glue.bmx" 'LUGI_CATEGORIES="scriptable" 'GenerateGlueCode("scriptable_glue.bmx") 'End Type Scriptable {expose disablenew category="scriptable"} Field _state@Ptr Field _closure%=LUA_NOREF Method Delete() Dispose End Method Method Init:Scriptable(state@Ptr) {hidden} _state = state Return Self End Method Method Activate() If _state And _closure <> LUA_NOREF Then lua_rawgeti(_state, LUA_REGISTRYINDEX, _closure) lua_pushbmaxobject(_state, Self) Local error:Int = lua_pcall(_state, 1, 0, 0) Assert error = 0 Else.. "The world has collapsed, you are our only hope! ("+error+"; "+lua_tostring(_state, -1)+")" EndIf End Method Method Dispose() If _state And _closure <> LUA_NOREF Then luaL_unref(_state, LUA_REGISTRYINDEX, _closure) _closure = LUA_NOREF EndIf End Method Method ToString$() Return "Scriptable" End Method End Type 'metadata isn't used since there's currently no way to use reflection to grab it for functions anyway Function l_Scriptable_SetScript%(L@Ptr) {bindto="Scriptable" as="SetScript"} Local so:Scriptable = Scriptable(lua_tobmaxobject(L, 1)) If so._closure <> LUA_NOREF Then If lua_isnoneornil(L, 2) Then luaL_unref(L, LUA_REGISTRYINDEX, so._closure) so._closure = LUA_NOREF ElseIf lua_isfunction(L, 2) Then lua_pushvalue(L, 2) lua_rawseti(L, LUA_REGISTRYINDEX, so._closure) EndIf ElseIf lua_isfunction(L, 2) Then lua_pushvalue(L, 2) so._closure = luaL_ref(L, LUA_REGISTRYINDEX) EndIf End Function BindFunctionToType(l_Scriptable_SetScript, "SetScript", TTypeID.ForName("Scriptable")) --v Bear in mind that this requires the most recent version of LuGI's master branch, since I added a handy method for binding glue functions to types. This was already possible, it just required you to be aware of the private API, which seems like a bad idea to me since it's only documented in the headers. This could also be easily ported to some other languages (C#, C++, maybe Objective-C and Java, etc. - basically, any language that is fairly flexible). I could probably cut out the use of LuGI, but LuGI makes working with objects very easy, so I choose to use it over making it more complex but completely standalone.

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