Reorder and Move NSTableView Row with NSPasteboard - nstableview

Question

I have an NSTableView where I can drag and drop table rows to reorder them. This works by setting a drag type in my view controller:
#IBOutlet weak var tableView: NSTableView!
let dragType = NSPasteboard.PasteboardType(rawValue: "myapp.task")
override func viewDidLoad() {
super.viewDidLoad()
tableView.registerForDraggedTypes([dragType])
}
...and then implementing the reordering with these table delegate methods:
//Start drag
func tableView(_ tableView: NSTableView, pasteboardWriterForRow row: Int) -> NSPasteboardWriting? {
let item = NSPasteboardItem()
item.setString(String(row), forType: dragType)
return item
}
//Verify proposed drop
func tableView(_ tableView: NSTableView, validateDrop info: NSDraggingInfo, proposedRow row: Int, proposedDropOperation dropOperation: NSTableView.DropOperation) -> NSDragOperation {
if dropOperation == .above {
return .move
}else{
return []
}
}
//Accept drop of one or multiple rows
func tableView(_ tableView: NSTableView, acceptDrop info: NSDraggingInfo, row: Int, dropOperation: NSTableView.DropOperation) -> Bool {
var oldIndexes = [Int]()
info.enumerateDraggingItems(options: [], for: tableView, classes: [NSPasteboardItem.self], searchOptions: [:]) { dragItem, _, _ in
if let str = (dragItem.item as! NSPasteboardItem).string(forType: self.dragType), let index = Int(str) {
oldIndexes.append(index)
}
}
//Do a bunch of logic to reorder the table rows...
}
Now, in addition to reordering my table rows, I want to be able to drag a row and drop it somewhere else in my app--sort of like moving the row to a different place.
I have a custom NSView set up as the drag destination for this, and I can drag a table row and the custom view reacts appropriately with a table row dragged over it:
class MyCustomView: NSView{
required init?(coder: NSCoder) {
super.init(coder: coder)
let taskDragType = NSPasteboard.PasteboardType(rawValue: "myapp.task")
registerForDraggedTypes([taskDragType])
}
override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
//...
}
override func draggingExited(_ sender: NSDraggingInfo?) {
//...
}
}
But the part I'm unclear on is how to get the table row, and its associated object set as a property on the NSTableCellView, when the drop occurs:
//This is another method in MyCustomView
override func performDragOperation(_ draggingInfo: NSDraggingInfo) -> Bool {
guard let items = draggingInfo.draggingPasteboard.pasteboardItems else{ return false }
for item in items{
print("---")
print(item) //<-- NSPasteboardItem
let index = item.propertyList(forType: NSPasteboard.PasteboardType(rawValue: "myapp.task"))
print(index) //<-- Index of the table row
//How can I also get the task object associated with the row?
}
}
I can get the index of the row, but what I need is the entire object from the row's data source so I can take action on the object it represents. My suspicion is that I need to change how I'm using pasteboardWriterForRow to put my object on the pasteboard, but I'm unsure how to do that.
How can I pass both the row index and the object to the pasteboard?

Answer 1

Soon after posting this, I decided to try something crazy, and it turns out I found a way to make this a lot simpler. It seems that NSPasteboard is really only necessary if you need to get stuff into and out of your app. Since I am just moving something from one part of my app to another, I can use the drag and drop delegate methods as events and handle the data myself.
First, I set up a global array for adding dragged task objects:
var draggedTasks = [Task]()
Whenever a task is dragged from my NSTableView, I add them to the array in the aforementioned delegate method where dragging starts:
//Start drag
func tableView(_ tableView: NSTableView, pasteboardWriterForRow row: Int) -> NSPasteboardWriting? {
//Queue tasks for moving to phases or projects
draggedTasks.append(tasks[row])
//Queue row for reordering
let item = NSPasteboardItem()
item.setString(String(row), forType: dragType)
return item
}
Then where I accept the drop in MyCustomView, I take action on the draggedTasks array:
//Save dropped tasks
override func performDragOperation(_ draggingInfo: NSDraggingInfo) -> Bool {
//Do stuff to draggedTasks based on the context of where they are dropped
return true
}
This is much simpler than going down the NSPasteboard route. 🙂