ActiveCoder provides a missing feature of Xcode --- bookmark. Even better, it creates bookmarks automatically for you. You just launch this app and use Xcode as you normally would. Whenever you want to open the file you opened or edited, you simply click the bookmark icon sitting on the status bar of your Mac. Consequently, ActiveCoder will show you a list of files and workspaces you have been working on. One double click is all it takes to instantly resume your work on a file.