Singleton獲取CoreData，在[fetchedResultsController_ performFetch：＆error]上崩潰

Question

我構建了一個應用程序來通過WLAN發送OSC消息。
這就是爲什麼我有一個「網絡」實體與一個單一的對象。造成這種情況的原因是，我想要一個Singleton來獲取這個對象。
在AppDelegate中我創建了一個類方法來獲取ManagedObjectContext

static NSManagedObjectContext* manObCon; 

@implementation... 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { 
    manObCon = self.managedObjectContext; 
... 
} 

+ (NSManagedObjectContext*) getManObCon{ 
    return manObCon; 
} 

的managedObjectContext到來，在我單身的地址，所以我認爲它應該工作。
Singleton.h（這裏沒有什麼特別）

#import <Foundation/Foundation.h> 
#import <CoreData/CoreData.h> 
#import "OSC_iPadAppDelegate.h"; 
#import "Network.h"; 

@interface NetworkSingleton : NSObject <NSFetchedResultsControllerDelegate> { 
} 
+ (Network*) getNetwork; 
+ (void) insertNewObject; 
+ (NSFetchedResultsController *)fetchedResultsController; 
@end 

Singleton.m應用程序崩潰AT [fetchedResultsController_ performFetch:&error]與

warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148)/Symbols/usr/lib/info/dns.so (file not found). 
Program received signal: 「EXC_BAD_ACCESS」. 
warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148)/Symbols/Developer/usr/lib/libXcodeDebuggerSupport.dylib (file not found). 
kill 
quit 

繼承人Singleton.m準則

#import "NetworkSingleton.h" 
static Network* _network; 
static NSFetchedResultsController *fetchedResultsController_; 
static NSManagedObjectContext *managedObjectContext_; 

@implementation NetworkSingleton 

+ (Network*) getNetwork{ 
    managedObjectContext_ = [OSC_iPadAppDelegate getManObCon]; //get the managedObjectContex from AppDelegate 
//fetchedResultsController init 
    fetchedResultsController_ = [NetworkSingleton fetchedResultsController]; //get fetchedResultsController 
//check if _network is set 
    if (_network == nil) { 
     id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController_ sections] objectAtIndex:0]; 
//if not set, check if there is already an network object in coredata 
     if ([sectionInfo numberOfObjects] == 0) { 
      //Create new Networkobject, if no one is existing 
      [NetworkSingleton insertNewObject]; 
      fetchedResultsController_ = nil; 
     } 
//set _network 
     _network = [fetchedResultsController_ objectAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]]; 
    } 
    return _network; 
} 

+ (NSFetchedResultsController *)fetchedResultsController { 

    if (fetchedResultsController_ != nil) { 
     return fetchedResultsController_; 
    } 

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Network" inManagedObjectContext: managedObjectContext_]; 
    [fetchRequest setEntity:entity]; 

    [fetchRequest setFetchBatchSize:1]; 

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"sourcePort" ascending:YES selector:nil]; 
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; 

    [fetchRequest setSortDescriptors:sortDescriptors]; 

    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext_ sectionNameKeyPath:nil cacheName:nil]; 
    aFetchedResultsController.delegate = self; 
    fetchedResultsController_ = aFetchedResultsController; 

    [aFetchedResultsController release]; 
    [fetchRequest release]; 
    [sortDescriptor release]; 
    [sortDescriptors release]; 

    NSError *error = nil; 
    /* 
    APP CRASHES HER 
    */ 
    if (![fetchedResultsController_ performFetch:&error]) { 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    } 

    return fetchedResultsController_; 
}  
@end 

所以我不知道爲什麼fetchedResultsController_不是他最擅長的 - 取得
它不是零，但我不能瞭解ErrorMessage，並且找不到Google或其他地方的任何東西。
問題可能是，我需要自己初始化fetchedResultsController，因爲它不會像生成的視圖控制器中那樣自動初始化。

感謝您的幫助

Answer 1

NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext_ sectionNameKeyPath:nil cacheName:nil]; 

fetchedResultsController_ = aFetchedResultsController; 

[aFetchedResultsController release]; 

當你的代碼塊它已經被釋放後使用fetchedResultsController_。因爲你分配了它（retainCount + 1），然後你釋放它（retainCount-1）。當您將FetchedResultsController分配給fetchedResultsController_時，您沒有保留。

要麼保留它像這樣fetchedResultsController_ = [aFetchedResultsController retain];
或刪除線[aFetchedResultsController release];

---

編輯：我剛纔看到，有可能是在你的代碼錯誤的。

您應該將fetchedResultsController以外的所有fetchedResultsController_替換爲self.fetchedResultsController。通常情況下，變量的後面或前面應該告訴你，除非你確定自己在做什麼，否則應該使用setter和getter。

而fetchedResultsController_ = [NetworkSingleton fetchedResultsController];調用fetchedResultsController_ = aFetchedResultsController;。
哪個可以工作，但我不會這樣做。