NSFetchedResultsController和多對多關係無法正常工作

Question

好的，我在過去的1-2週中一直在尋找並嘗試這種情況，但我沒有得到它的工作。我可以在沒有NSFRC的情況下達到我想要的水平，但是出於性能原因和快速考慮，我希望能夠與NSFRC一起完成。 所以，我有2個實體的DataModel - 看到圖片

有一個帳戶，一個帳戶可以有多個accountchanges - 這是相當明顯的。 所以我希望能夠選擇一個帳戶，然後顯示該特定帳戶的所有AccountChanges。 到目前爲止，我能夠獲得帳戶，並訪問cellForRow函數中的NSSet，但我沒有得到正確的部分和numberOfRowsInSection - 這是主要問題。

下面是一些代碼：

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 
} 

有一些打印報表時僅供參考！

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，我能夠獲得數據，但始終只有一個項目，而不是整個集 - 我想由於該段/ numberOfRows是錯誤的。

這裏是我的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! 
} 

我假設它是SortDescriptor或謂語 - 或者兩者兼而有之？

任何幫助或至少指示，非常感謝。 我已經嘗試了很多不同的方法，但都沒有給我正確的結果。

Answer 1

我會做相反的，我的意思是使用FRC來獲取所有與某個ID帳戶的變化，並使用以下斷言：

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

或

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

我會重新將Accounts實體重命名爲Account，因爲這是一對一的關係，所以將關係重命名爲Account。 這就是假設你有一個包含所有帳戶的表格視圖，並且當你點擊一個表格時，它會讓你回到它的更改。

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! 
} 

乾杯