Xcode plist files consistently forget type designations

I have numerous Plist files that contains dictionaries in a project and I find that they reliably forget the data type of various entries and default to NSString.

For example, I might have a PLIST containing a di开发者_如何学运维ctionary with several keys set to a type of NSNumber, and after closing and reopening Xcode they all get defaulted to NSString.

Is this a known issue? Is there a way I can avoid it? Changing the types of dozens of values every time I restart Xcode gets pretty annoying.

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This is an Xcode 3 bug. The file itself does not actually get corrupted, Xcode merely interprets the file wrongly. Numbers are still numbers and the app treats them as such, but Xcode reports them as strings when opened from the Group Tree.