It turns out that you need to subclass NSTableViewDiffableDataSource and implement the drag and drop API in that subclass. It's kinda weird, but that is what needs to be done.
In my case, what I did was this:
implement all my drag and drop API that I usually would in my MyViewController
subclass NSTableViewDiffableDataSource to MyDiffableDataSource
added delegate APIs to MyDiffableDataSource that would ask the delegate for the drag and drop code. For example, it would do something like this:
in the MyDiffableDataSource.h file I would have this:
@class MyDiffableDataSource;
@protocol MyDiffableDataSourceDelegate <NSObject>
- (nullable id <NSPasteboardWriting>)tableView:(NSTableView *)tableView
pasteboardWriterForRow:(NSInteger)row;
- (void)tableView: (NSTableView *)tableView
draggingSession: (NSDraggingSession *)session
willBeginAtPoint: (NSPoint)screenPoint
forRowIndexes: (NSIndexSet *)rowIndexes;
- (NSDragOperation)tableView: (NSTableView *)tableView
validateDrop: (id <NSDraggingInfo>)draggingInfo
proposedRow: (NSInteger)row
proposedDropOperation: (NSTableViewDropOperation)dropOperation;
- (BOOL)tableView: (NSTableView *)tableView
acceptDrop: (id <NSDraggingInfo>)draggingInfo
row: (NSInteger)row
dropOperation: (NSTableViewDropOperation)dropOperation;
- (void)tableView: (NSTableView *)tableView
draggingSession: (NSDraggingSession *)session
endedAtPoint: (NSPoint)screenPoint
operation: (NSDragOperation)operation;
@end
@interface MyDiffableDataSource : NSTableViewDiffableDataSource
@property (weak, nonatomic, readwrite) id <MyDiffableDataSourceDelegate> delegate;
@end
In the MyDiffableDataSource.m file, it would do something like this:
- (nullable id <NSPasteboardWriting>)tableView:(NSTableView *)tableView
pasteboardWriterForRow:(NSInteger)row
{
if ([self.delegate respondsToSelector: @selector(tableView:pasteboardWriterForRow:)]){
return [self.delegate tableView: tableView
pasteboardWriterForRow: row];
}
return nil;
}
.
.
.
etc
I did not want to have drag and drop code in different classes, which I why I implemented step 2 and 3 using delegate messaging. Of course, I would need MyViewController to be set as the delegate of MyDiffableDataSource.
Too bad there is no real documentation that easily goes over this. You have to guess it when reading that NSTableViewDIffableDataSource conforms to NSTableViewDataSource.
EH
