LuaJIT ObjC bridge

tlc.lua

The bridge is now located at https://github.com/fjolnir/TLC

You're welcome :-)

Some more suggestions:

I removed all assignments from the fast path, and added a cache for the class names as well (with weak keys).

I also rewrote the column appending code, with the assumption that there is at most one trailing column. More readable and efficient this way, but it doesn't notice when people pass too many parameters (beside the first one). Since this check is only performed the first time a method is called, I supposed that I could drop it.

On the same topic:

I'm not very familiar with ObjC, so I may be wrong, but isn't it possible to have both msg and msg: as distinct messages on the same class? If yes, then the current caching behavior is flawed, and you'd have to make trailing underscores mandatory (if you want to keep the doc simple g), witch is ugly, but you may not have the choice...

This is 100% untested (typed in the browser).

local _empty = {}
local _cacheMT = {__mode = 'k'}
local _classNameCache = setmetatable({}, _cacheMT) 
-- you may want to do the same for the other caches.

ffi.metatype("struct objc_class", {
    __index = function(self,selArg)
        local cached = (
            _classMethodCache[ 
                _classNameCache[self]
            ] 
            or _empty --no need to create a new table each time.
        )[selArg]
        if cached ~= nil then
            return cached
        end

        -- Else
        return function(...)
            local selStr = selArg:gsub("_", ":")

            -- Append missing colons to the selector
            if select('#',...) ~= 0 and selStr:sub(-1, -1) ~= ":" then 
                selStr = selStr .. ":"
            end

            if _log then _log("Calling +["..className.." "..selStr.."]") end

            local method
            local methodDesc = C.class_getClassMethod(self, SEL(selStr))
            if methodDesc ~= nil then
                method = _readMethod(methodDesc)
            else
                method = C.objc_msgSend
            end

            -- Cache the calling block and execute it
            _classNameCache[self] = _classNameCache[self] or ffi.string(C.class_getName(self))
            local className = _classNameCache[self] 
            _classMethodCache[className] = _classMethodCache[className] or {}
            _classMethodCache[className][selArg] = function(self, ...)
                if self == nil then
                    return nil -- Passing nil to self means crashing
                end

                local success, ret = pcall(method, ffi.cast("id", self), SEL(selStr), ...)
                if success == false then
                    error(ret.."\n"..debug.traceback())
                end

                if ffi.istype("struct objc_object*", ret) and ret ~= nil then
                    if (selStr:sub(1,5) ~= "alloc" and selStr ~= "new")  then
                        ret:retain()
                    end
                    if selStr:sub(1,5) ~= "alloc" then
                        ret = ffi.gc(ret, C.CFRelease)
                    end
                end
                return ret
            end
            return _classMethodCache[className][selArg](...)
        end
    end,

Edit: I also updated my log function suggestion above to make it more robust. table.concat doesn't generate the intermediate strings, which otherwise have to be interned and collected.

Edit2 : These are still globals (and should be defined with ffi.typeof() according to Mike Pall. I'm not familiar with the FFI, but I suppose he's right g)

CGPoint = ffi.metatype("CGPoint", {})
CGSize = ffi.metatype("CGSize", {})
CGRect = ffi.metatype("CGRect", {})
CGAffineTransform = ffi.metatype("CGAffineTransform", {})
NSRange = ffi.metatype("NSRange", {})

Fixed cache.
Added option to toggle automatically appending underscores on selectors(enabled by default)
Moved CG types from global to objc namespace
Added __tostring to objects and selectors so you can now print() them directly
fixes

Added convenience functions to convert lua values to objects. NSArr(), NSDic(), NSNum(), NSStr() and the general Obj() which type checks and calls the correct function