iphone - 重置 CoreData 持久存储

Question

基本上，我想做的是清除 CoreData 持久存储中的所有数据，然后导入新数据。你会怎么做？看来最简单的解决方案是调用 [NSPersistentStoreCoordinator removePersistentStore:error:] 然后删除文件。这是可用的最佳实践吗？它是线程安全的吗？

非常感谢，

#

问题0.1:是

我正在尝试更新 CoreData 持久存储中的数据。我的用户正在看到带有统计数据的表格 View 。我想通过删除所有现有数据然后导入新数据来更新应用程序。我想显示一个进度 View 来告诉用户应用程序没有挂起。

我在我的AppDelegate中添加了以下resetPersistentStore方法(给出persistentStoreCoordinator供引用):

// ...
@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
// ...

/**
 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 = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: kPersistentStoreFilename]];

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

    return persistentStoreCoordinator;
}

/**
 * Will remove the persistent store
 */
- (NSPersistentStoreCoordinator *)resetPersistentStore {
    NSError *error;

    [managedObjectContext lock];

    // FIXME: dirty. If there are many stores...
    NSPersistentStore *store = [[persistentStoreCoordinator persistentStores] objectAtIndex:0];

    if (![persistentStoreCoordinator removePersistentStore:store error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }  

    // Delete file
    if (![[NSFileManager defaultManager] removeItemAtPath:store.URL.path error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    } 

    // Delete the reference to non-existing store
    [persistentStoreCoordinator release];
    persistentStoreCoordinator = nil;

    NSPersistentStoreCoordinator *r = [self persistentStoreCoordinator];
    [managedObjectContext unlock];

    return r;
}

然后在我看来我这样做了(在另一个线程中，因为我正在使用 MBProgressHUD:

PatrimoineAppDelegate *appDelegate = (PatrimoineAppDelegate *)[[UIApplication sharedApplication] delegate]; 
// Delete everything
[appDelegate resetPersistentStore];

我得到一个 EXC_BAD_ACESS...

我不太了解 CoreData 或多线程，也许我犯了一个明显的错误......

Answer 1

对于那些在 iOS9+ 上尝试执行此操作的用户，现在提供了 destroyPersistentStoreAtURL 和 replacePersistentStoreAtURL API。