NSTableView won't call viewForTableColumn

Question

I am trying to build a table view without interface builder from scratch in my Cocoa app and my viewForTableColumn method refuses to get called.

My table view is created using this code.

let tableView: NSTableView = {
    let table = NSTableView(frame: .zero)
    table.headerView = nil
    table.addTableColumn(NSTableColumn(identifier: .column))

    return table
}()

I also have this extension for the NSUserInterfaceItemIdentifier class

extension NSUserInterfaceItemIdentifier {
    static let cell = NSUserInterfaceItemIdentifier("cell")
    static let column = NSUserInterfaceItemIdentifier("column")
}

My view controller is implementing NSTableViewDataSource and NSTableViewDelegate and they are set in the viewDidLoad method. The table view is also into a scroll view.

let scrollView = NSScrollView()

override func viewDidLoad() {
    self.scrollView.documentView = self.tableView
    self.scrollView.hasVerticalScroller = true
    self.view.addSubview(self.scrollView)

    self.tableView.delegate = self
    self.tableView.dataSource = self
    self.tableView.reloadData() // To make sure the method would be called.
}

The value returned from the numberOfRows method is bigger than 0 and is executed.

From my understanding the following method should be called with the row parameter ranging from 0 to the value returned by numberOfRows but it's never being called.

func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? {
    guard let view = self.tableView.makeView(withIdentifier: .cell, owner: self) as? NSTableCellView else {
        return nil
    }

    // set the text/font for the view

    return view
}

I've also tried using dataCellFor and rowViewForRow but none of them is getting called.

EDIT:

I've checked the frame of my elements to make sure the table view and the rows were visible.

Answer 1

According to one of the comments beneath your question tableView(_:viewFor:row:) is being called, it's just returning nil. This makes sense given your implementation of that method. When makeViewWithIdentifier fails you need to manually create the relevant view and return it, rather than returning nil. As such your implementation should look something like this:

func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? {

    if let recycledView = self.tableView.makeView(withIdentifier: .cell, owner: self) as? NSTableCellView {
        return recycledView
    } else {
        // create view from scratch
        let newCell = NSTableCellView()
        newCell.identifier = NSUserInterfaceItemIdentifier.cell
        // customise here...
        return newCell
    }
}

Look again at the link I provided in my comment, you'll see that that implementation never returns nil from this method.