NSOutlineView, how to get the selected cell - swift

Question

I want to get the selected cell from the NSOutlineView control. I found a solution here: How can I get the selected cell from a NSOutlineView?. It says
Use the delegate. willDisplayCell: is called when a cell changes its selection state.
However when I test it, I found that my willDisplayCell: is not be called.
Here's my code, it can be run normally, but the willDisplayCell: method has never been called. Where did I make a mistake? Thanks.
class TreeNode: NSObject{
var name: String = ""
private(set) var isLeaf: Bool = false
var children: [TreeNode]?
init(name: String, isLeaf: Bool){
self.name = name
self.isLeaf = isLeaf
if !isLeaf{
children = [TreeNode]()
}
}
}
class ViewController: NSViewController {
#IBOutlet weak var sourceList: NSOutlineView!
private var data = TreeNode(name: "Root", isLeaf: false)
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
for i in 0..<10{
let node = TreeNode(name: "name \(i)", isLeaf: i % 2 == 0)
data.children?.append(node)
}
}
}
extension ViewController: NSOutlineViewDataSource {
func outlineView(_ outlineView: NSOutlineView, numberOfChildrenOfItem item: Any?) -> Int {
if let item = item as? TreeNode, !item.isLeaf {
return item.children!.count
}
return 1
}
func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool {
return !((item as? TreeNode)?.isLeaf ?? false)
}
func outlineView(_ outlineView: NSOutlineView, child index: Int, ofItem item: Any?) -> Any {
if let item = item as? TreeNode {
if item.isLeaf{
return item
}else{
return item.children![index]
}
}
return data
}
}
extension ViewController: NSOutlineViewDelegate {
func outlineView(_ outlineView: NSOutlineView, willDisplayCell cell: Any, for tableColumn: NSTableColumn?, item: Any) {
print("called")
}
func outlineView(_ outlineView: NSOutlineView, viewFor tableColumn: NSTableColumn?, item: Any) -> NSView? {
let cell: NSTableCellView?
if let item = item as? TreeNode{
cell = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "DataCell"), owner: self) as? NSTableCellView
cell?.textField?.stringValue = item.name
}else{
cell = nil
}
return cell
}
}

Answer 1

I've solved this problem myself. The following code is how to get the selected cell:
func getSelectedCell() -> NSTableCellView? {
if let view = self.sourceList.rowView(atRow: self.sourceList.selectedRow, makeIfNecessary: false) {
return view.view(atColumn: self.sourceList.selectedColumn) as? NSTableCellView
}
return nil
}
Now I can access the NSTextField control by the code getSelectedCell()?.textField.