使用NSFetchedResultsController对描述符进行排序 – Swift

我有一个UITableView从Core Data提供,NSFetchedResultsController返回Location实体.默认排序(和节标题)是通过实体名称的第一个字母.这是有效的(尽管我仍然试图将大小写合并到相同的部分.)用户可以选择按三个可选类别之一(实体的属性)对表进行排序,然后对这些类别进行排序按实体名称.

当我设置按类别排序时,我得到以下运行时错误：

[_TtCSs23_ContiguousArrayStorage00007F80513B59D0 key]: unrecognized selector sent to instance 0x7f80513b5720

这是我的NSFetchedResultsController：

var sectionNameKeyPathString1: String?
var sectionNameKeyPathString2: String?

var fetchedResultsController: NSFetchedResultsController {
    if _fetchedResultsController != nil {
        return _fetchedResultsController!
    }

    let fetchRequest = NSFetchRequest()
    // Edit the entity name as appropriate.
    let entity = NSEntityDescription.entityForName("Location",inManagedObjectContext: self.managedObjectContext!)
    fetchRequest.entity = entity

    // Set the batch size to a suitable number.
    fetchRequest.fetchBatchSize = 20

    // Edit the sort key as appropriate.
    if sectionNameKeyPathString1 != nil {
        let sortDescriptor1 = NSSortDescriptor(key: sectionNameKeyPathString1!,ascending: true)
        let sortDescriptor2 = NSSortDescriptor(key: sectionNameKeyPathString2!,ascending: true)
        let sortDescriptors = [sortDescriptor1,sortDescriptor2]
        fetchRequest.sortDescriptors = [sortDescriptors]
    } else {
        let sortDescriptor = NSSortDescriptor(key: "locationName",ascending: true)
        fetchRequest.sortDescriptors = [sortDescriptor]
    }

    var sectionNameKeyPath: String
    if sectionNameKeyPathString1 == nil {
        sectionNameKeyPath = "firstLetterAsCap"
    } else {
        sectionNameKeyPath = sectionNameKeyPathString1!
    }

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,managedObjectContext: self.managedObjectContext!,sectionNameKeyPath: sectionNameKeyPath,cacheName: "Locations")
    aFetchedResultsController.delegate = self
    _fetchedResultsController = aFetchedResultsController

    var error: NSError? = nil
    if !_fetchedResultsController!.performFetch(&error) {
        // TODO: Handle this error
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application,although it may be useful during development.
        //println("Unresolved error (error),(error.userInfo)")
        abort()
    }

    return _fetchedResultsController!
}

使用断点我很有信心,例如,sectionNameKeyPathString1 =“category1”和sectionNameKeyPathString2 =“locationName”以及sectionNameKeyPath =“category1”,因此键路径与第一个排序描述符匹配.

我有这个在Obj-C工作,但现在我把我的头发拉出来,确定我患有虫病.

let sortDescriptors = [sortDescriptor1,sortDescriptor2] // <- an [NSSortDescriptor]
    fetchRequest.sortDescriptors = [sortDescriptors] // <- now an [[NSSortDescriptor]]

fetchRequest.sortDescriptors = [sortDescriptor1,sortDescriptor2]