我需要刪除所有用戶信息並重新創建它。我用它來創造一切的代碼在應用程序的委託:重新創建CoreData時的上下文問題
- (NSManagedObjectContext *)managedObjectContext {
if (managedObjectContext != nil) {
return managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return managedObjectContext;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (persistentStoreCoordinator != nil) {
return persistentStoreCoordinator;
}
NSString* dir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) lastObject];
NSURL *storeURL = [NSURL fileURLWithPath: [dir stringByAppendingPathComponent:
@"Data.sqlite"]];
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;
}
然後,我刪除了一切:
[context reset];
NSString* dir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) lastObject];
NSURL *storeURL = [NSURL fileURLWithPath: [dir stringByAppendingPathComponent:
@"Data.sqlite"]];
NSError *error;
NSURL *storeURL = store.URL;
NSPersistentStoreCoordinator *storeCoordinator = [((CustomAppDelegate *)[[UIApplication sharedApplication] delegate]) persistentStoreCoordinator];
NSPersistentStore *store = [[storeCoordinator persistentStores] objectAtIndex:0];
[storeCoordinator removePersistentStore:store error:&error];
[[NSFileManager defaultManager] removeItemAtPath:storeURL.path error:&error];
[storeCoordinator release];
storeCoordinator = nil;
而且似乎工作,問題是當我嘗試保存新數據,之後。如果我這樣做:
NSManagedObjectContext *afterContext = [appDelegate managedObjectContext];
NSEntityDescription *userEntity = [NSEntityDescription entityForName:@"User"
inManagedObjectContext:afterContext];
NSManagedObject *user = [NSEntityDescription
insertNewObjectForEntityForName:[userEntity name] inManagedObjectContext:afterContext];
[user setValue:@"John" forKey:@"firstName"];
if(![afterContext save:&error])
NSLog(@"oops");
崩潰在afterContext保存,它gaves我EXC_BAD_INSTUCTION例外。當我做 [appDelegate managedObjectContext]它創建新的persistentStore,所以我不知道可能是什麼問題。對前一個對象的引用?堆棧跟蹤根本沒有提供任何線索。
感謝您的提示!讓所有事情都在委託中進行並設置上下文無(之後重新創建)解決了所有問題。 PS:你的回答讓我想到了指針,爲什麼我需要在代表中這麼做,真的如此:謝謝! – ferostar