NSFetchedResultsController和多对多关系无法正常工作

Question

好的，我在过去的1-2周中一直在寻找并尝试这种情况，但我没有得到它的工作。我可以在没有NSFRC的情况下达到我想要的水平，但是出于性能原因和快速考虑，我希望能够与NSFRC一起完成。 所以，我有2个实体的DataModel - 看到图片

有一个帐户，一个帐户可以有多个accountchanges - 这是相当明显的。 所以我希望能够选择一个帐户，然后显示该特定帐户的所有AccountChanges。 到目前为止，我能够获得帐户，并访问cellForRow函数中的NSSet，但我没有得到正确的部分和numberOfRowsInSection - 这是主要问题。

下面是一些代码：

func numberOfSections(in tableView: UITableView) -> Int { 

    print("Sections : \(self.fetchedResultsController.sections?.count)") 
    if (self.fetchedResultsController.sections?.count)! <= 0 { 
     print("There are no objects in the core data - do something else !!!") 
    } 
    return self.fetchedResultsController.sections?.count ?? 0 
} 

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
    print("Section Name") 
    print(self.fetchedResultsController.sections![section].name) 
    let sectionInfo = self.fetchedResultsController.sections![section] 
    print("Section: \(sectionInfo) - Sections Objects: \(sectionInfo.numberOfObjects)") 
    return sectionInfo.numberOfObjects 
} 

有一些打印报表时仅供参考！

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 

    let myCell = myTable.dequeueReusableCell(withIdentifier: "myCell")! as UITableViewCell 
    let accountBalanceChanges = self.fetchedResultsController.object(at: indexPath) 
    print("AccountBalanceChanges from cell....") 
    print(accountBalanceChanges) 

    let details = accountBalanceChanges.accountchanges! as NSSet 
    print("Print out the details:") 
    print(details) 
    let detailSet = details.allObjects 
    let detailSetItem = detailSet.count // Just for information! 


    let myPrint = detailSet[indexPath.row] as! AccountChanges 
    let myVal = myPrint.category 

    myCell.textLabel?.text = myVal 

    return myCell 
} 

所以，我能够获得数据，但始终只有一个项目，而不是整个集 - 我想由于该段/ numberOfRows是错误的。

这里是我的NSFRC

var fetchedResultsController: NSFetchedResultsController<Accounts> { 
    if _fetchedResultsController != nil { 
     return _fetchedResultsController! 
    } 
    let fetchRequest: NSFetchRequest<Accounts> = Accounts.fetchRequest() 
    // Set the batch size to a suitable number. 
    fetchRequest.fetchBatchSize = 20 
    // Edit the sort key as appropriate. 

    let sortDescriptor = NSSortDescriptor(key: "aName", ascending: false) 
    fetchRequest.sortDescriptors = [sortDescriptor] 


    let predicate = NSPredicate(format: "(ANY accountchanges.accounts = %@)", newAccount!) 
    fetchRequest.predicate = predicate 
    // 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.coreDataStack.context, sectionNameKeyPath: nil, cacheName: nil) 
    aFetchedResultsController.delegate = self 
    _fetchedResultsController = aFetchedResultsController 

    do { 
     try _fetchedResultsController!.performFetch() 
    } catch { 
     // Replace this implementation with code to handle the error appropriately. 
     // fatalError() 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. 
     let nserror = error as NSError 
     fatalError("Unresolved error \(nserror), \(nserror.userInfo)") 
    } 

    return _fetchedResultsController! 
} 

我假设它是SortDescriptor或谓语 - 或者两者兼而有之？

任何帮助或至少指示，非常感谢。 我已经尝试了很多不同的方法，但都没有给我正确的结果。

Answer 1

我会做相反的，我的意思是使用FRC来获取所有与某个ID帐户的变化，并使用以下断言：

let predicate = NSPredicate(format: "accounts.aId = %@", ACCOUNTID) 

或

let predicate = NSPredicate(format: "accounts = %@", account.objectID) 

我会重新将Accounts实体重命名为Account，因为这是一对一的关系，所以将关系重命名为Account。 这就是假设你有一个包含所有帐户的表格视图，并且当你点击一个表格时，它会让你回到它的更改。

var fetchedResultsController: NSFetchedResultsController<AccountChanges> { 
    if _fetchedResultsController != nil { 
     return _fetchedResultsController! 
    } 
    let fetchRequest: NSFetchRequest<AccountChanges> = AccountChanges.fetchRequest() 
    // Set the batch size to a suitable number. 
    fetchRequest.fetchBatchSize = 20 
    // Edit the sort key as appropriate. 

    let sortDescriptor = NSSortDescriptor(key: "aName", ascending: false) 
    fetchRequest.sortDescriptors = [sortDescriptor] 


    let predicate = NSPredicate(format: "accounts.aId = %@", ACCOUNTID) 
    fetchRequest.predicate = predicate 
    // 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.coreDataStack.context, sectionNameKeyPath: nil, cacheName: nil) 
    aFetchedResultsController.delegate = self 
    _fetchedResultsController = aFetchedResultsController 

    do { 
     try _fetchedResultsController!.performFetch() 
    } catch { 
     // Replace this implementation with code to handle the error appropriately. 
     // fatalError() 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. 
     let nserror = error as NSError 
     fatalError("Unresolved error \(nserror), \(nserror.userInfo)") 
    } 

    return _fetchedResultsController! 
} 

干杯