不调用 NSFetchedResultsControllerDelegate 委托方法

Posted 2023-03-13

【中文标题】不调用 NSFetchedResultsControllerDelegate 委托方法

【英文标题】：NSFetchedResultsControllerDelegate delegates methods are not called

【发布时间】：2016-06-05 23:01:17

【问题描述】：

这是我的代码：

class FetchResultControllerDataProvider: NSObject, NSFetchedResultsControllerDelegate 

    private let fetchedResultController: NSFetchedResultsController
    private var delegate: TodayViewController!

    init(fetchedResultController: NSFetchedResultsController, delegate: TodayViewController) 
        self.fetchedResultController = fetchedResultController
        self.delegate = delegate

        super.init()
        self.fetchedResultController.delegate = self
        try! self.fetchedResultController.performFetch()
    

    func controllerWillChangeContent(controller: NSFetchedResultsController) 
        print("Controller will change")
    

    func controllerDidChangeContent(controller: NSFetchedResultsController) 
        print("COntroller did changed")
    

    func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) 
        print("Controller did change section")
    

    func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) 
        print("Controller did change object at indexpath")
    



func loadData() 
    let request = NSFetchRequest(entityName: Transaction.entityName)
    request.predicate = Transaction.defaultPredicate
    request.sortDescriptors = []
    request.returnsObjectsAsFaults = false
    request.fetchBatchSize = 20

    let frc = NSFetchedResultsController(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
    let dataProvider = FetchResultControllerDataProvider(fetchedResultController: frc, delegate: self)
    dataSource = TableViewDataSource(tableView: self.tableView, dataProvider: dataProvider, delegate: self)

当我添加数据时，FetchResultControllerDataProvider 中的任何方法都不会被调用。但我不知道为什么。

有人可以帮我吗？

编辑：

添加数据：

func addTransaction() 
    self.context.performChanges 
        Transaction.insert(self.context, name: self.name.text!, amount: Double(self.amount.text!)!, type: self.currentTypeTag)
    

public func saveOrRoleback() -> Bool 

    do 
        try save()
        return true
     catch 
        rollback()
        return false
    


public func performChanges(block: () -> ()) 

    performBlockAndWait 
        block()
        self.saveOrRoleback()
    

所以这部分代码被调用了，并没有抛出错误。 但是我试图检查核心数据sql文件，它似乎是空的。所以没有添加数据。

【问题讨论】：

你试过删除 super.init() 吗？

您在代码的哪个位置添加数据？也许您需要包含更多代码。

什么是保留实例？是直接销毁吗？

@Wain：由dataSource对象保留。

开启线程调试。展示您如何添加数据。显示一切运行的顺序。

【参考方案1】：

添加数据时，您需要检查委托和 fetchedResultsController 对象是否仍然存在并正确填充。您可以尝试打印这些变量的值吗？

self.fetchedResultController

self.fetchedResultController.delegate

在您添加数据时，您的PersistentStore 中是否插入了数据？

【参考方案2】：

    NSFetchRequest *fetchRequest11 = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity1 = [NSEntityDescription entityForName:@"RemainderDataBase" inManagedObjectContext:[self managedObjectContext]];
    [fetchRequest11 setEntity:entity1];
    NSPredicate *p1=[NSPredicate predicateWithFormat:@"startdate < %@", [NSDate date]];
    [fetchRequest11 setPredicate:p1];
    NSError *fetchError;
    NSError *error;
    NSArray *fetchedProducts1=[managedObjectContext executeFetchRequest:fetchRequest11 error:&fetchError];
    for (NSManagedObject *product in fetchedProducts1)
    
        [managedObjectContext deleteObject:product];
        [tableview reloadData];
    
    [managedObjectContext save:&error];
    [self.tableview reloadData];


 self.FRC = [[NSFetchedResultsController alloc]initWithFetchRequest:fetchRequest managedObjectContext:[self managedObjectContext] sectionNameKeyPath:nil cacheName:nil];

    self.FRC.delegate = self;

    NSError *fetchingErr=nil;

    if ([self.FRC performFetch:&fetchingErr])
    
        NSLog(@"Succesfully Fetched data from RemainderDataBase");
    
    else
    
        NSLog(@"Failed To Fetch data from RemainderDataBase");
    

设置获取请求以检索您的数据

注意： 正确设置代表..

并在 ViewDidLoad 中添加这些行

id delegate = [[UIApplication sharedApplication] delegate];
    self.managedObjectContext = [delegate managedObjectContext];