NSDocument duplicate problem

The aim is to save the data of a program in 2 different formats of choice, say type1 (default) and type2. No problem when + (BOOL)autosavesInPlace is NO, you can save as… and get a choice. No problem when + (BOOL)autosavesInPlace is YES and you created a new document, you can choose when saving. But you do not get a choice when you created the new file by duplicating a existing file. It takes the type of the latter. (Using dataOfType:error:, but did not find a solution either by using writeToURL:ofType:error:, duplicateDocument:, etc.)

NSDocument duplicate problem
 
 
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