Question

关于'不访问'sqlite DB的澄清：上下文/商店不能仅在设备上检测.sqlite中的任何条目，尽管NSBundle具有.sqlite并且.sqlite的文件大小正确。在模拟器中，上下文/存储工作正常。

我很难过。我在我的xcdatamodeld中添加了一个模型版本。我重置了版本，让我的代码自动进行迁移，并重新填充我的数据库。

在iPhone模拟器上，它可以工作。但是，在运行设备时，它无法从数据库中读取。

我已经输入代码来检测sqllite实际上是在设备上还是验证文件大小。正在从NSBundle正确复制SQLLite，以及指示存在数据的文件大小。

不知何故，我的代码拒绝访问设备上的数据库。知道为什么会这样吗？访问数据库的代码没有改变 - 唯一改变的是数据模型。以下代码适用于升级前的设备。

// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
- (NSManagedObjectContext *)managedObjectContext
{
if (_managedObjectContext != nil) {
    return _managedObjectContext;
}

NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
    _managedObjectContext = [[NSManagedObjectContext alloc] init];
    [_managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return _managedObjectContext;
}

// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
- (NSManagedObjectModel *)managedObjectModel
{
  if (_managedObjectModel != nil) {
    return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"sirona" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}

// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (_persistentStoreCoordinator != nil) {
    return _persistentStoreCoordinator;
}

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

NSString *databasePath = [NSBundle.mainBundle pathForResource:@"sirona" ofType:@"sqlite"];
NSLog(@"File manager: %@", [[NSFileManager defaultManager] contentsOfDirectoryAtPath:[[NSBundle mainBundle] bundlePath] error:nil]);
NSDictionary *attrs = [[NSFileManager defaultManager] attributesOfItemAtPath: @"sirona.sqlite" error: NULL];
UInt32 result = [attrs fileSize];
NSLog(@"File size: %d", (unsigned int)result);
NSError *error = nil;

// important part starts here
   NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                            [NSNumber numberWithBool:YES],NSMigratePersistentStoresAutomaticallyOption,
                            [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                                                           nil];

_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}

return _persistentStoreCoordinator;
}

我如何通过核心数据访问数据库：

  NSFetchRequest *request = [[NSFetchRequest alloc] init];
  [request setEntity:[NSEntityDescription entityForName:@"Representative" inManagedObjectContext:context]];
  [request setIncludesSubentities:NO]; //Omit subentities. Default is YES (i.e. include subentities)

  NSError *err;
  NSUInteger count = [context countForFetchRequest:request error:&err];
  NSLog(@"Count: %lu", (unsigned long)count);

编辑：如果没有将代码复制到设备的代码，不确定这是如何工作的。但它现在似乎在起作用。

执行此操作的代码：

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

if (![[NSFileManager defaultManager] fileExistsAtPath:[storeURL path]]) {
    NSURL *preloadURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"sirona" ofType:@"sqlite"]];
    NSLog(@"PreloadURL: %@", preloadURL);
    NSError* err = nil;

    if (![[NSFileManager defaultManager] copyItemAtURL:preloadURL toURL:storeURL error:&err]) {
        NSLog(@"Oops, could copy preloaded data");
    }
}

NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

Answer 1

在初始化CoreData上下文之前，您必须将sqlite文件复制到您具有读/写权限的文件夹

设备上的核心数据无法访问sqlite DB

1 个答案: