NSArray to plist on mac

I need to save/load a NSMutableArray 开发者_如何学Cof NSDictionarys to a file in the application directory. Apparently this does not work like on the iPhone ([array writeToFile] & arrayWithContensOfFile]). How is this done on a mac. Thank you. (sorry for the stupid question)

The problem was that I had a NSAttributedString in the dictionary . Apperently this can not be saved to a plist.