Singleton获取CoreData，在[fetchedResultsController_ performFetch：＆error]上崩溃

Question

我构建了一个应用程序来通过WLAN发送OSC消息。
这就是为什么我有一个“网络”实体与一个单一的对象。造成这种情况的原因是，我想要一个Singleton来获取这个对象。
在AppDelegate中我创建了一个类方法来获取ManagedObjectContext

static NSManagedObjectContext* manObCon; 

@implementation... 

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

+ (NSManagedObjectContext*) getManObCon{ 
    return manObCon; 
} 

的managedObjectContext到来，在我单身的地址，所以我认为它应该工作。
Singleton.h（这里没有什么特别）

#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应用程序崩溃AT [fetchedResultsController_ performFetch:&error]与

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 

继承人Singleton.m准则

#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 

所以我不知道为什么fetchedResultsController_不是他最擅长的 - 取得
它不是零，但我不能了解ErrorMessage，并且找不到Google或其他地方的任何东西。
问题可能是，我需要自己初始化fetchedResultsController，因为它不会像生成的视图控制器中那样自动初始化。

感谢您的帮助

Answer 1

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

fetchedResultsController_ = aFetchedResultsController; 

[aFetchedResultsController release]; 

当你的代码块它已经被释放后使用fetchedResultsController_。因为你分配了它（retainCount + 1），然后你释放它（retainCount-1）。当您将FetchedResultsController分配给fetchedResultsController_时，您没有保留。

要么保留它像这样fetchedResultsController_ = [aFetchedResultsController retain];
或删除线[aFetchedResultsController release];

---

编辑：我刚才看到，有可能是在你的代码错误的。

您应该将fetchedResultsController以外的所有fetchedResultsController_替换为self.fetchedResultsController。通常情况下，变量的后面或前面应该告诉你，除非你确定自己在做什么，否则应该使用setter和getter。

而fetchedResultsController_ = [NetworkSingleton fetchedResultsController];调用fetchedResultsController_ = aFetchedResultsController;。
哪个可以工作，但我不会这样做。