預加載核心數據數據庫不工作

Question

我在一個應用程序中創建了一個核心數據庫，它涉及從API中抽取信息並填充數據庫。

我現在想在另一個應用程序中使用它。

我已經複製了.xcdatamodeld文件和NSManagedObject類。

我已經添加並導入了Core Data框架。

我已將.sqlite文件複製到我的新應用程序資源中作爲默認數據庫。

我正在使用下面的代碼，它應該將默認數據庫複製到Documents目錄並打開它，以便我可以對其執行查詢。

它導致應用程序崩潰，沒有錯誤信息，對我要去哪裏錯誤的任何想法？

如果我在這裏使用saveToURL創建數據庫，我知道文件名將是persistentStore而不是Trailer.sqlite，如下所示，是否相關？

感謝

- (void)viewDidLoad 
{ 
[super viewDidLoad]; 


// Get URL -> "<Documents Directory>/<TrailerDB>" 
NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; 

url = [url URLByAppendingPathComponent:@"TrailerDB"]; 

UIManagedDocument *doc = [[UIManagedDocument alloc] initWithFileURL:url]; 

// Copy out default db to documents directory if it doesn't already exist 
NSFileManager *fileManager = [NSFileManager defaultManager]; 

if (![fileManager fileExistsAtPath:[url path]]) { 
    NSString *defaultDB = [[NSBundle mainBundle] 
            pathForResource:@"trailerdatabase" ofType:@"sqlite"]; 
    if (defaultDB) { 

     [fileManager copyItemAtPath:defaultDB toPath:[url path] error:NULL]; 

    } 
} 

if (doc.documentState == UIDocumentStateClosed) { 

    // exists on disk, but we need to open it 
    [doc openWithCompletionHandler:^(BOOL success) 
    { 

     if (success) [self useDatabase:doc]; 

     if (!success) NSLog(@"couldn’t open document at %@", url); 


    }]; 

} else if (doc.documentState == UIDocumentStateNormal) 
{ 
    [self useDatabase:doc]; 
} 

} 

Answer 1

Ive有另一個樣子，我不知道你在做什麼，但下面這段代碼是我做的，將回答你的問題。我檢查工作數據庫是否存在，以及它是否不從應用程序包移動到位，然後繼續加載它。我留下了蘋果模板中的股票評論，因爲我認爲他們最終可能會有所幫助。

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator 
{ 
    if (__persistentStoreCoordinator != nil) 
    { 
     return __persistentStoreCoordinator; 
    } 

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"workingDataBase.sqlite"]; 

    NSError *error = nil; 

    if (![[NSFileManager defaultManager] fileExistsAtPath:[[self applicationDocumentsDirectoryString] stringByAppendingPathComponent: @"workingDataBase.sqlite"]]){ 
     //database not detected 
     NSLog(@"database not detected"); 
     NSURL * defaultDatabase = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"DefaultData" ofType:@"sqlite"]]; 
     NSError * error; 
     if (![[NSFileManager defaultManager] copyItemAtURL:defaultDatabase toURL:storeURL error:&error]){ 
      // Handle Error somehow! 
      NSLog(@"copy file error, %@", [error description]); 
     } 
    } 

    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; 
    if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) 
    { 
     /* 
     Replace this implementation with code to handle the error appropriately. 

     abort() 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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. 

     Typical reasons for an error here include: 
     * The persistent store is not accessible; 
     * The schema for the persistent store is incompatible with current managed object model. 
     Check the error message to determine what the actual problem was. 


     If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory. 

     If you encounter schema incompatibility errors during development, you can reduce their frequency by: 
     * Simply deleting the existing store: 
     [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil] 

     * Performing automatic lightweight migration by passing the following dictionary as the options parameter: 
     [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; 

     Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details. 

     */ 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    }  

    return __persistentStoreCoordinator; 
}