根据轮换更改XIB文件的最佳方法？

My app has so far just been a portrait-based application. However, I am adding landscape mode to a new version, but have found that my XIB files look shocking when rotated from portrait to landscape. Apparently I need to make a landscape version of each XIB and use some code to change with XIB launches based on what rotation occurs. Am I right? If so, where do I go from here? Are there any Apple sample apps utilising this code?My app has so far just been a portrait-based ap