How to group tableView data using sectionNameKeyPath (Swift) - ios

Question

I've not been able to figure out how to do the following in Swift and looking for pointers.
I'm pulling string values from Core Data and displaying them in a UITableView...that's working and displaying all entries. I now want to 'group' these values by date created (also stored in Core Data) but am having a hard time implementing this group header...here's what I have:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var sound = self.sounds[indexPath.row]
var cell = UITableViewCell()
// Convert Date to String
var formatter: NSDateFormatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd-HH-mm-ss"
let dateTimePrefix: String = formatter.stringFromDate(sound.dateSaved)
// Display the following in each rows
cell.textLabel!.text = sound.name + " Saved: " + dateTimePrefix
return cell
}
Could someone point me in the right direction as to how to implement 'headers'? I already have the tableView in my Main.storyboard setup to 'Grouped' as a style.
--- Update
Thanks for the response below but, unfortunately, the examples are in Obj-C and I'm shooting for swift.
To expand, I have the following retrieving data from Core Data and displaying all in UITableView:
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.dataSource = self
self.tableView.delegate = self
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
var context = (UIApplication.sharedApplication().delegate as AppDelegate).managedObjectContext!
var request = NSFetchRequest(entityName: "Sound")
self.sounds = context.executeFetchRequest(request, error: nil)! as [Sound]
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.sounds.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell: UITableViewCell = UITableViewCell(style: UITableViewCellStyle.Subtitle, reuseIdentifier: "MyTestCell")
var sound = self.sounds[indexPath.row]
// Convert Date to String
var formatter: NSDateFormatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd # HH:mm:ss"
let dateTimePrefix: String = formatter.stringFromDate(sound.dateSaved)
// Display the following in each rows
cell.textLabel!.text = sound.name // Sound Name
// Display the following as each subtitles
cell.detailTextLabel!.text = dateTimePrefix // Sound Duration (Currently 'date')
return cell
}
Could someone point me in the right direction as to how I go about 'grouping' each by month with a 'month' header using sectionNameKeyPath, I believe? Specifically, which piece of code would need to be modified to break list into 'sections'.

Answer 1

Here are some pointers:
You need to use an NSFetchedResultsController ("FRC") - check out the documentation here. You will see that you specify the sectionNameKeyPath when initialising the FRC.
There is boilerplate code for updating a tableView using an FRC. The easiest way to get this, and observe how the FRC works, is to create a project using Apple's Master/Detail application template, ensuring you select the "Use Core Data" option. Play with it in that project to see how it works, and then cut/paste into your own project.
In your case, you want to the month (and presumably year?) as the section name. There are a few ways to do that, but the easiest is to create a function (eg. sectionIdentifier) in your Sound class which returns a string with the section name, in the format you desire, derived from the dateSaved. Then specify sectionNameKeyPath:sectionIdentifier when initialising the FRC.