How to match values in two TableViews - ios

Question

There is a tableview with folder names and after clicking on each row, it segues to another TableView to show sections and rows for each folder. But I got problem how to show values corresponding to every folder. The error message is: fatal error: unexpectedly found nil while unwrapping an Optional value. Please see my codes below. I guess the problem is prepareForSegue codes didn't work well.
Note: Somewhere I need to delete half ")" as it doesn't work for "()" and I can't edit. Please help to edit.
In first tableview:
var folderNames = [String]()
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == segueToDetailsTable {
let detailsVC = segue.destinationViewController as! DetailsViewController
detailsVC.detailsTableView.indexPathForCell(UITableViewCell(style: UITableViewCellStyle.Value1, reuseIdentifier: "DetailsCell")) == savingTableView.indexPathForSelectedRow
}
}
In second TableView to show details:
var sectionTitles = ["WebSite", "Date Saved", "Document Used","Add Notes"]
var detailsInSection = [[String](), [NSDate](),[AnyObject](),[String]()]
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return detailsInSection.count
}
func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return sectionTitles[section]
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return detailsInSection[section].count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("DetailsCell")
cell?.textLabel!.text = detailsInSection[indexPath.section][indexPath.row].description
return cell!
}

Answer 1

You're doing some weird stuff in prepareForSegue. detailsVC hasn't loaded yet thus the tableview may still be nil. But most importantly, you cant connect the tables like that. When you select a row, figure out what data should be shown in the next. After you've aggregated the data set it as a property on the second vc inside the prepareForSegue method. When the next vc loads the property that it is using should already be set when the table loads. You also have two different data sources that tableview reads from. This is a bit dangerous because you cant guarantee there be a corresponding value in the other source.