从UISearchController的筛选搜索结果中删除

Question

我有一个tableView从其中获取单元格内容CoreData并且已经用SearchDisplayController新的替换(已弃用)SearchController.我使用相同的tableView控制器来呈现对象的完整列表以及过滤/搜索的对象.

我设法使搜索/过滤工作正常,可以从过滤列表移动到这些项的详细视图,然后编辑并将更改成功保存回过滤的tableView.我的问题是滑动以从筛选列表中删除单元格导致运行时错误.之前SearchDisplayController我可以轻松地执行此操作,因为我可以访问SearchDisplayController's结果tableView,因此以下(伪)代码可以正常工作:

func controllerDidChangeContent(controller: NSFetchedResultsController) {
    // If the search is active do this
          searchDisplayController!.searchResultsTableView.endUpdates()
    // else it isn't active so do this
          tableView.endUpdates()
    }
}

不幸的是,没有这样的tableView暴露给UISearchController我和我不知所措.我曾尝试制作tableView.beginUpdates()和tableView.endUpdates()条件上的tableView不被搜索的tableView但没有成功.

为了记录这是我的错误消息:

Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-3318.65/UITableView.m:1582

*编辑*

我的tableView使用FetchedResultsController从CoreData填充自己.这个tableViewController也是SearchController用来显示过滤结果的那个.

var searchController: UISearchController!

然后在ViewDidLoad中

searchController = UISearchController(searchResultsController: nil)
searchController.dimsBackgroundDuringPresentation = false
searchController.searchResultsUpdater = self
searchController.searchBar.sizeToFit()
self.tableView.tableHeaderView = searchController?.searchBar
self.tableView.delegate = self
self.definesPresentationContext = true

和

func updateSearchResultsForSearchController(searchController: UISearchController) {
    let searchText = self.searchController?.searchBar.text
    if let searchText = searchText {
        searchPredicate = searchText.isEmpty ? nil : NSPredicate(format: "locationName contains[c] %@", searchText)
        self.tableView.reloadData()
    }
}

就错误信息而言,我不确定我能添加多少.按下通过滑动显示的红色删除按钮(仍然显示)后,应用程序立即挂起.这是1 - 5的线程错误日志.该应用程序似乎挂在4号.

#0  0x00000001042fab8a in objc_exception_throw ()
#1  0x000000010204b9da in +[NSException raise:format:arguments:] ()
#2  0x00000001027b14cf in -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] ()
#3  0x000000010311169a in -[UITableView _endCellAnimationsWithContext:] ()
#4  0x00000001019b16f3 in iLocations.LocationViewController.controllerDidChangeContent (iLocations.LocationViewController)(ObjectiveC.NSFetchedResultsController) -> () at /Users/neilmckay/Dropbox/Programming/My Projects/iLocations/iLocations/LocationViewController.swift:303
#5  0x00000001019b178a in @objc iLocations.LocationViewController.controllerDidChangeContent (iLocations.LocationViewController)(ObjectiveC.NSFetchedResultsController) -> () ()

我希望其中一些有所帮助.

*编辑2*

override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {
        let location: Location = self.fetchedResultsController.objectAtIndexPath(indexPath) as Location
        location.removePhotoFile()

        let context = self.fetchedResultsController.managedObjectContext
        context.deleteObject(location)

        var error: NSError? = nil
        if !context.save(&error) {
            abort()
        }
    }
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if self.searchPredicate == nil {
        let sectionInfo = self.fetchedResultsController.sections![section] as NSFetchedResultsSectionInfo
        return sectionInfo.numberOfObjects
    } else {
        let filteredObjects = self.fetchedResultsController.fetchedObjects?.filter() {
            return self.searchPredicate!.evaluateWithObject($0)
        }
        return filteredObjects == nil ? 0 : filteredObjects!.count
    }
}

// MARK: - NSFetchedResultsController methods

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)
        fetchRequest.sortDescriptors = [sortDescriptor1, sortDescriptor2]
    } else {
        let sortDescriptor = NSSortDescriptor(key: "firstLetter", ascending: true)
        fetchRequest.sortDescriptors = [sortDescriptor]
    }

    var sectionNameKeyPath: String
    if sectionNameKeyPathString1 == nil {
        sectionNameKeyPath = "firstLetter"
    } 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: nil /*"Locations"*/)
    aFetchedResultsController.delegate = self
    _fetchedResultsController = aFetchedResultsController

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

    return _fetchedResultsController!
}

var _fetchedResultsController: NSFetchedResultsController? = nil

func controllerWillChangeContent(controller: NSFetchedResultsController) {
    if searchPredicate == nil {
        tableView.beginUpdates()
    } else {
        (searchController.searchResultsUpdater as LocationViewController).tableView.beginUpdates()
    }

// tableView.beginUpdates()}

func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
    var tableView = UITableView()
    if searchPredicate == nil {
        tableView = self.tableView
    } else {
        tableView = (searchController.searchResultsUpdater as LocationViewController).tableView
    }

    switch type {
    case .Insert:
        tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
    case .Delete:
        tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
    default:
        return
    }
}

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath) {
    var tableView = UITableView()
    if searchPredicate == nil {
        tableView = self.tableView
    } else {
        tableView = (searchController.searchResultsUpdater as LocationViewController).tableView
    }

    switch type {
    case .Insert:
        println("*** NSFetchedResultsChangeInsert (object)")
        tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)

    case .Delete:
        println("*** NSFetchedResultsChangeDelete (object)")
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
    case .Update:
        println("*** NSFetchedResultsChangeUpdate (object)")
        if searchPredicate == nil {
            let cell = tableView.cellForRowAtIndexPath(indexPath) as LocationCell
            let location = controller.objectAtIndexPath(indexPath) as Location
            cell.configureForLocation(location)
        } else {
            let cell = tableView.cellForRowAtIndexPath(searchIndexPath) as LocationCell
            let location = controller.objectAtIndexPath(searchIndexPath) as Location
            cell.configureForLocation(location)
        }
    case .Move:
        println("*** NSFetchedResultsChangeMove (object)")
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
    }
}

func controllerDidChangeContent(controller: NSFetchedResultsController) {
    if searchPredicate == nil {
        tableView.endUpdates()
    } else {
        (searchController.searchResultsUpdater as LocationViewController).tableView.endUpdates()
    }
}

Answer 1

出现问题的原因是获取的结果控制器使用的indexPath与tableView中相应行的indexPath不匹配.

搜索控制器处于活动状态时,将重用现有的tableView来显示搜索结果.因此,您的逻辑是区分两个tableViews:

if searchPredicate == nil {
    tableView = self.tableView
} else {
    tableView = (searchController.searchResultsUpdater as LocationViewController).tableView
}

没必要.它可以工作,因为你searchController.searchResultsUpdater = self初始化searchController时设置,所以不需要改变它,但在任何一种情况下都使用相同的tableView.

不同之处在于在searchController处于活动状态时填充tableView的方式.在这种情况下,它(从numberOfRowsInSection代码中)看起来好像过滤结果都显示在一个部分中.(我假设cellForRowAtIndexPath工作方式类似.)假设您删除了筛选结果中第0行第7行的项目.然后commitEditingStyle将使用indexPath调用0-7,并且以下行:

let location: Location = self.fetchedResultsController.objectAtIndexPath(indexPath) as Location

将尝试从FRC获取索引0-7处的对象.但FRC索引0-7处的项目可能是完全不同的对象.因此,您删除了错误的对象.然后触发FRC委托方法,并告诉tableView删除索引0-7处的行.现在,如果真正删除的对象不在筛选结果中,那么即使删除了一行,行数仍将保持不变:因此错误.

因此,要解决此问题,请修改您的内容,commitEditingStyle以便在searchController处于活动状态时找到要删除的正确对象:

override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {
        var location : Location
        if searchPredicate == nil {
            location = self.fetchedResultsController.objectAtIndexPath(indexPath) as Location
        } else {
            let filteredObjects = self.fetchedResultsController.fetchedObjects?.filter() {
                return self.searchPredicate!.evaluateWithObject($0)
            }
            location = filteredObjects![indexPath.row] as Location
        }
        location.removePhotoFile()

        let context = self.fetchedResultsController.managedObjectContext
        context.deleteObject(location)

        var error: NSError? = nil
        if !context.save(&error) {
            abort()
        }
    }
}

我无法测试上述情况; 如果出现一些错误,请道歉.但它至少应指向正确的方向; 希望能帮助到你.请注意,在某些其他tableView委托/数据源方法中可能需要进行类似的更改.