我正在使用Core Data和iCloud开发一个日记应用。核心数据模型的简化视图如下所示：
[期刊]＆lt; - ＆gt;＆gt; [发布]＆lt; - ＆gt;＆gt; [内容]
我使用NSFetchedResultControllers使用＆＃39;内容＆＃39;来填充UITableView，并使用＆＃39; Journals＆＃39;来填充UICollectionView。从模型。
表视图工作正常，只要添加或删除内容更改，就会调用获取的结果控制器委托。但是，在集合视图控制器中，当添加新日志或其中的帖子或内容发生变化时，获取的结果控制器不会调用委托（我知道最后一部分可能是预期的，因为日志对象本身并没有改变） 。但是，在删除期刊时会调用该委托。
我希望每当插入期刊时都会调用该代表，并且在没有运气或进一步了解情况的情况下与这个问题搏斗数小时。
获取的结果控制器已初始化并配置如下：
// property declaration
lazy var fetchedResultsController: NSFetchedResultsController = self.initialFetchedResultsController()
// initialization
func initialFetchedResultsController() -> NSFetchedResultsController {
let request = NSFetchRequest(entityName: "Journal")
let nameSort = NSSortDescriptor(key: "name", ascending: true)
request.sortDescriptors = [nameSort]
return return NSFetchedResultsController(fetchRequest: request, managedObjectContext: DataModel.sharedModel().managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
}
// configuration, called in viewDidLoad()
func configureFetchedResultsController() {
fetchedResultsController.delegate = collectionViewFetchedResultsControllerDelegate
do {
try fetchedResultsController.performFetch()
print("fetching")
} catch {
fatalError("Failed to initialize FetchedResultsController: \(error)")
}
}
在配置期间传递给fetchedResultsController的collectionViewFetchedResultsControllerDelegate是管理此视图控制器的集合视图的标准NSFetchedResultsControllerDelegate。
当删除数据时，在共享数据模型中调用以下方法，导致fetchedResultsController调用其委托（我只是通过向所有委托方法添加一些调试打印语句来断言）。
func deleteJournal(journal: Journal) {
// delete all posts attached to journal
deletePostsForJournal(journal)
// delete journal
managedObjectContext.deleteObject(journal)
saveManagedObjectContext()
}
func deletePostsForJournal(journal: Journal) {
// delete all content attached to posts of journal
deleteContentForJournal(journal)
// delete all posts attached to journal
performBatchDeleteForJournal(journal, deleteEntityName: "Post", predicateFormat: "journal == %@")
}
func deleteContentForJournal(journal: Journal) {
// delete all content attached to posts of journal
performBatchDeleteForJournal(journal, deleteEntityName: "Content", predicateFormat: "post.journal == %@")
// delete all images attached to posts of journal
performBatchDeleteForJournal(journal, deleteEntityName: "Image", predicateFormat: "post.journal == %@")
}
private func performBatchDeleteForJournal(journal: Journal, deleteEntityName entityName: String, predicateFormat: String) {
let fetchRequest = NSFetchRequest(entityName: entityName)
fetchRequest.predicate = NSPredicate(format: predicateFormat, journal)
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try persistentStoreCoordinator.executeRequest(deleteRequest, withContext: managedObjectContext)
} catch let error as NSError {
print("Could not execute batch delete fetch request \(error), \(error.userInfo)")
}
saveManagedObjectContext()
}
但是，当我通过使用下面的insert方法插入新日志来更新模型时，不会调用fetchedResultsController。
func createJournal(name: String) {
// creates or returns (if already existing) a journal from the managed object context
journalForName(name)
saveManagedObjectContext()
}
func journalForName(name: String) -> Journal {
// configures fetch request
let fetchRequest = NSFetchRequest()
let entityDescription = NSEntityDescription.entityForName("Journal", inManagedObjectContext: managedObjectContext)
fetchRequest.entity = entityDescription
// configures predicate to match posts with date
fetchRequest.predicate = NSPredicate(format: "name == %@", name)
// executes fetch request
do {
let result = try self.managedObjectContext.executeFetchRequest(fetchRequest)
if let journal = result.first as? Journal {
return journal
}
} catch let error as NSError {
print("Could not execute fetch request from managedObjectContext \(error), \(error.userInfo)")
}
// creates a new journal since one doesn't exist with this name
let journal = Journal(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext)
journal.name = name
return journal
}
如果已经存在具有相同名称的日志，则实现journalForName方法仅创建新日记。
插入工作并在模型中更新，因为如果重新启动应用程序，则会显示创建的日记。我非常感谢你解决这个问题的任何帮助！感谢。