Swift - Sorting an array retrieved from Core Data [duplicate]

问题

I want to sort the array with usernames that I retrieve from my core data. I retrieve it like this:

override func viewDidAppear(animated: Bool) {

    let appDel:AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context:NSManagedObjectContext = appDel.managedObjectContext!
    let freq = NSFetchRequest(entityName: "User")
    let en = NSEntityDescription.entityForName("User", inManagedObjectContext: context)

    myList = context.executeFetchRequest(freq, error: nil)!

    tv.reloadData()

}

And later I set the cells in my tableview like this:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let CellID:NSString = "cell"
    var cell: UITableViewCell = self.tv.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
    if let ip = indexPath as Optional {

        var data:NSManagedObject = myList[ip.row] as NSManagedObject

        cell.textLabel!.text = data.valueForKeyPath("username") as String!

    }

I tried to use the sorting function for in the viewDidAppear function like this:

 var sortedList = myList.sorted { $0.localizedCaseInsensitiveCompare($1) == NSComparisonResult.OrderedAscending }

But this gives me an error saying: "Could not find member 'localizedCaseInsensitiveCompare'"

Any suggestions on how to proceed would be appreciated.

回答1:

I like to use a separate function to fetch and sort the array. You sort the array by using an NSSortDescriptor. You can add the capitalization check as a selector for the sort descriptor. I got the separate function idea from this tutorial. I used it and it works for me. I got the idea for the selector idea by referencing this Objective-C code.

var objectives: [NSManagedObject]!
func fetchUsernames() {

    static let appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context: NSManagedObjectContext = appDel.managedObjectContext!

    let freq = NSFetchRequest(entityName: "User")
    let sortDescriptor = NSSortDescriptor(key: "username", ascending: true, selector: "localizedCaseInsensitiveCompare:")
    freq.sortDescriptors = [sortDescriptor]

    do {
        let fetchedResults: [NSManagedObject] = try managedContext.executeFetchRequest(freq) as! [NSManagedObject]
        if let results: [NSManagedObject] = fetchedResults {
            objectives = results
        }
    } catch let error as NSError {
        print("Error: \(error.localizedDescription)")
    }
    tableView.reloadData()
}

回答2:

executeFetchRequest returns [AnyObject]? and you need to convert this as [NSManagedObjet] array and sort on user key

if let myList = myList as? [NSManagedObject] {
   var sortedList = myList.sorted { ($0.valueForKeyPath("user") as String).localizedCaseInsensitiveCompare(($1.valueForKeyPath("user") as String)) == NSComparisonResult.OrderedAscending }
}
else {

   println("My List not contains the NSManagedObject array")
}

来源：https://stackoverflow.com/questions/27649464/swift-sorting-an-array-retrieved-from-core-data

标签

ios

arrays

sorting

core-data

swift