什么是适用于iOS和Mac OS X的跨平台方法?

There seem to be lots of answers for cross-platform frameworks for devices (iPhone + Android), and cross-platform frameworks for desktops (Mac + Win + Linux). This is a different question regarding a suitable framework, methodology, template app, tutorial, or just helpful hints, on developing native apps (not just web apps) that are cross-platform portable between a device OS and a desktop OS.There seem to be lots of answers for cross-plat