Simplified.swift

gistfile1.txt

func tableView(_ tableView: NSTableView, objectValueFor tableColumn: NSTableColumn?, row: Int) -> 
    guard let obj = (self.representedObject as? ModelType)?.collection(at:row) else {
        return nil
    }
    switch tableColumn?.identifier.rawValue ?? "" {
    case "column1":
        return obj.field1
    case "column2":
        return objc.field2
    //...
    default:
        return nil
    }
}