I thought there was no decent AS3/ActionScript3 code editor for Mac (FlashDevelop is only for Windows) but I found this old tutorial on CreativeApplications that recommends TextMate2 as a code editor for AS3/Flixel on Mac.
Turns out as I have OSX 10.9/Mavericks I must use TextMate3 instead of TextMate2 and the tutorial for using Flex is intended for TextMate2 therefore doesn’t work for TextMate3… and there isn’t enough documentation yet for this version (still alpha).
Found out there is a handy ActionScript 3 package for SublimeText2, a code editor that I really like and the package is installable with SublimeText2 package control. You just need to add then a BuildSystem to it afterwards:
Simply navigate to your ST2 preferences > Browse Packages and then find the ActionScript 3 directory and add the contents of this gist to a new file named actionscript.sublime-build (change the SDK location to where the SDK is on your machine). Once you have compiled your SWF you can then run the SWF within the Flash Player using Shift + ⌘ + B (shift + cmd + B).
Now you can open an .AS file that uses Flixel and it will compile to a nice .swf file. I simply used “the Macintosh Flash Player 11.9 Projector content debugger (DMG, 15.44MB)” to run my .swf’s but it seems there is lot more solutions : [best tools for debugging flash ActionScript 3] when it comes to debugging.