I was using a Windows VM for ZX-IDE - great IDE, but I'd rather dev for the spectrum on MacOS.  I couldn't find IDE though, and I'd rather enjoyed the ZX-IDE on Windows.  I've made a really basic IDE to get me going - if I improve it enough I'll make it available.

1) It uses ZASM as the compiler. There is actually a Mac OS  Xcompiled version already, which you can download here:

http://k1.dyndns.org/Develop/projects/zasm/distributions/

2) I've created a really basic editor in XCode, and if you click the 'Compile' button it reports back any errors, and if everything is fine then runs your program in Fuse:

http://fuse-emulator.sourceforge.net/

3) The final stage is to get your coding running a really Spectrum.  ZASM creates TAP files rather than TZX, but Fuse can save the file in TZX format.  It's then just a case of running PlayZX (see previous post about that) to create and play a sound file that can be loaded on a really Spectrum.