I like XCode, and I use it to edit all of my source for SymPy. But, like many editors, it likes to auto-indent new lines to the level of indentation of the previous line. This is a useful feature, but it makes for training whitespace out the wazoo, since blank lines will be indented in. I am constantly finding myself using SymPy’s strip_whitespace script to clean up my files.
This bugged me enough that I Googled a solution, and found this. It is a simple XCode plugin that, among other things, adds an option to strip trailing whitespace on save. Just install in the PlugIns folder in the XCode package and enable the option in the new Google pane of the XCode preferences.