is there a way to "hook" into the OSX Finder to perform the following:
When my Application starts, the User sees a Folder in his Finder which is created by my application. Inside this Folder the User sees Files from several Folders...a unified view to several Files in several Folders that the User specified in my Application. So, in this "Unified Folder" are not the real Files, they are still in there original Folder but the User sees them in this one Folder as if there were all his real Files in this new Folder. So there is no copying or moving involved.
To be honest, I've no Idea if it's possible and what I should looking for inside the Cocoa SDK. Maybe there is an API for the Finder itself or some other way?!
Regards
twickl
First option is your application could create aliases to the original files. The Finder will show these with a small arrow "badge" over the icon, so it is clear they are not the original files but aliases of them.
If you don't like the badges on the icons creating hard links may give you what you want.
Mac OS X presents a view of the HFS+ (Mac) filesystem which matches the UFS (Unix) one and you have access to hard and symbolic links. The latter are treated by the Finder similar to aliases but the former are indistinguishable from the original files as they are the original files - under the Unix filesystem a file in a directory is just a reference (the inode number) to the real file, each entry in a directory is just a hard link to the actual file, and a file can have any number of hard links to it (a file is deleted when the link count drops to 0, think of the retain/release model if that helps).
At the Cocoa level NSFileManager has methods to create hard links, or you can use the Unix level link(2) function.