Create a "get files Window"which allows to import files

The class you need to use is called NSOpenPanel. This class is a subclass of NSSavePanel (thus, it inherits all methods and properties from that class). Click the API reference links above for all methods and properties of the open panel.

Here is some pseudocode to get you started:

1. Create a new NSOpenPanel instance.
2. Set properties (allowedFileTypes, allowsMultipleSelection, showsHiddenFiles, etc.)
3. Present the panel in a window with beginSheetModal(for:completionHandler:) or by itself with begin(completionHandler:).
4. Inside the handler, check if the result is equal to NSFileHandlingPanelOKButton.
5. Retrieve the file URLs with the urls property.

Feel free to ask if you need any additional help! 🙂

How would I go about creating a space where to show the files icons once they have been selected? As of now I was constructing that area as an image view with a white picture as background, is that the correct container to show the files' icons after selecting them?

I recommend using an NSCollectionView instead. Here is an great Swift tutorial (see raywenderlich.com/145978/nscollectionview-tutorial) that shows how to use NSCollectionView. You can then use the URLs from the NSOpenPanel to populate the NSCollectionView. Also, you can use NSURL's getResourceValue(_:forKey:) method with the key effectiveIconKey to get the file's icon.

I am gonna go ahead and give this a try, thank you for all the help!