ios - 使用 Core Data Swift 对 TableView 和行进行分段

Question

我在 sqlite 中有两个表:

代码由 XCode Generation 生成:

class Event: NSManagedObject {

    @NSManaged var startDate: NSDate
    @NSManaged var details: EventDetail  //i think this property shoud be var details Array<EventDetail>  am i correct?
}

class EventDetail: NSManagedObject {

    @NSManaged var title: String
    @NSManaged var location: String
    @NSManaged var note: String
    @NSManaged var endDate: NSDate
    @NSManaged var event: NSManagedObject
}

我想将事件放在 section 中，将 eventDetails 放在 rows 中。

我创建了加载事件的方法:

var eventList : Array<AnyObject> = []

func loadEvents(){
    let appDel : AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let moc: NSManagedObjectContext = appDel.managedObjectContext!
    let eventMO = NSFetchRequest(entityName: "Event")
    eventMO.returnsObjectsAsFaults = false

    var err : NSErrorPointer = nil
    eventList = moc.executeFetchRequest(eventMO, error: err)!
    self.tblEvento.reloadData()
}

func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
    return eventList.count
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {       
    //return (eventList[section] as Event).details.count
   return //????? what can i put here
}

我不知道我可以在方法 numbertOfRowsInSection 中放入什么来定义该部分的行数。因为我无法访问 details.count 或类似的内容。

我认为还有其他方法可以做到这一点。我看到一些东西使用 NSFetchedResultsController 但没有成功。

我希望得到一些帮助。

Answer 1

只是一个提示:如果您正在使用 CoreData 和 UiTableView，请使用 NSFetchedResultsController 使事情变得非常非常容易。如果您正在寻找起点和示例代码 - 只需在 Xcode 中创建一个新的主从应用程序项目并在对话框中打开“使用核心数据”。

现在，直接回答您的问题:NSFetchResultsController 的“实现”示例:

var fetchedResultsController: NSFetchedResultsController {

  if _fetchedResultsController != nil {
       return _fetchedResultsController!
   }
   let fetchRequest = NSFetchRequest()
   // Edit the entity name as appropriate.
   let entity = NSEntityDescription.entityForName("Event", inManagedObjectContext: self.managedObjectContext!)
   fetchRequest.entity = entity

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

   // Edit the sort key as appropriate.
   let sectionSortDescriptor = NSSortDescriptor(key: "startDate", ascending: true)
   let secondSortDescriptor = NSSortDescriptor(key: "title", ascending: true)

   let sortDescriptors = [sectionSortDescriptor, secondSortDescriptor]

   fetchRequest.sortDescriptors = sortDescriptors

   // 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: "startDate", cacheName: nil)
   aFetchedResultsController.delegate = self
   _fetchedResultsController = aFetchedResultsController

   var error: NSError? = nil
   if !_fetchedResultsController!.performFetch(&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!
}

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return self.fetchedResultsController.sections?.count ?? 0
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    let sectionInfo = self.fetchedResultsController.sections![section] as NSFetchedResultsSectionInfo
    return sectionInfo.numberOfObjects
}