问题
In older versions of Xcode (before Xcode 4.1), hitting ESC would give a very useful autocomplete window, including the return value of any methods available. However, in XCode 4.1, hitting ESC gives a much less useful autocomplete helper. It dos not give the return value of methods, and only lists methods and variables which have already been utilized in the current file. Is there a way to get back the old functionality, which was much more useful?
回答1:
Try deleting derived data folder which holds the project's index information (classes & methods employed in the project) and reopening the project. Doing so will kick in the indexer of Xcode.
Path to derived data folder can be found in Organizer's (Cmd+Shift+2) Projects tab.
来源：https://stackoverflow.com/questions/7461895/xcode-does-not-give-any-useful-information-in-autocomplete