Inscrutable Swift/Xcode Errors

Ugh, what a horrible day of coding. I've been playing around with a small Swift app that's using Core Data and displaying the contents in a Table View.

There are plenty of tutorials on Swift + Core Data on the web but the majority were written before Apple released the 'final' version of the language with Beta 6 so any and all code samples you see online have to be audited as you use them. Today I discovered that you need to use that same auditing mentality when you're using Apple's boilerplate code as well.

Xcode will generate a lot of boilerplate code when you chose certain project templates when you begin a new project. It so happens that if you choose the Master-Detail Application template and choose "Use Core Data" you'll get a starting point for the very app I was wanting to build.

Since the purpose of this app was to learn all of the ins and outs of Core Data access using Swift I decided to use the boilerplate code as a reference but rewrite it all myself.

The problems started while overriding the controller:didChangeObject method. Using Xcode's autocomplete I wrote the following code:

    // MARK: FetchedResultsControllerDelegate
    func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
        switch type {
        case .Insert:
            tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
        default:
            return
        }
    }

I was getting a weird error for tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade):

Could not find member 'Fade'

What?

If I replaced .Fade with nil I then got:

'(UITableView, numberOfRowsInSection: Int) -> Int' does not have a member named 'insertRowsAtIndexPaths'

WHAT DOES THAT EVEN MEAN?

This is the code in the boilerplate I was working from:

    func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath) {
        switch type {
            case .Insert:
                tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
            case .Delete:
                tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
            case .Update:
                self.configureCell(tableView.cellForRowAtIndexPath(indexPath)!, atIndexPath: indexPath)
            case .Move:
                tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
                tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
            default:
                return
        }
    }

Notice the difference? It took me a couple of hours of debugging to see it.

It's the method signature, in the auto generated code newIndexPath and indexPath are optionals and in the boilerplate they aren't.

If this helps out one other person I will be happy.

Bug report time.