您知道有什么方法可以删除存储在Core Data中的所有条目吗?我的schema应该保持不变;我只想把它重置为空白。
Edit
我希望以编程方式做到这一点,这样用户就可以基本上按下重置按钮。
您知道有什么方法可以删除存储在Core Data中的所有条目吗?我的schema应该保持不变;我只想把它重置为空白。
Edit
我希望以编程方式做到这一点,这样用户就可以基本上按下重置按钮。
当前回答
MagicalRecord使这非常简单。
[MyCoreDataObject MR_truncateAll];
其他回答
Swift 5.1解决方案
public static func reset() {
let coordinator = _persistentContainer.persistentStoreCoordinator
for store in coordinator.persistentStores where store.url != nil {
try? coordinator.remove(store)
try? FileManager.default.removeItem(atPath: store.url!.path)
}
}
iOS 10+的更新解决方案
使用NSBatchDeleteRequest删除实体中的所有对象,而不必将它们加载到内存中或遍历它们。
// create the delete request for the specified entity
let fetchRequest: NSFetchRequest<NSFetchRequestResult> = MyEntity.fetchRequest()
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
// get reference to the persistent container
let persistentContainer = (UIApplication.shared.delegate as! AppDelegate).persistentContainer
// perform the delete
do {
try persistentContainer.viewContext.execute(deleteRequest)
} catch {
print(error.localizedDescription)
}
此代码已更新为iOS 10和Swift 3。如果你需要支持iOS 9,请看这个问题。
来源:
核心数据:删除实体的所有实例的最快方法(包括Objective-C代码) Core Data的新内容(WWDC 2015视频) Core Data的新内容(WWDC 2016视频) 如何在iOS 10中使用核心数据 Core Data Swift 3.0有什么新功能
Swift 4/5, iOS 9+
重新构建整个CoreData SQLite文件将确保擦除所有数据,因此删除所有实体。只需调用deleteAndRebuild()。
class CoreDataStack {
// Change this
static let datamodelName = "ProjectName"
static let storeType = "sqlite"
static let persistentContainer = NSPersistentContainer(name: datamodelName)
private static let url: URL = {
let url = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask)[0].appendingPathComponent("\(datamodelName).\(storeType)")
assert(FileManager.default.fileExists(atPath: url.path))
return url
}()
static func loadStores() {
persistentContainer.loadPersistentStores(completionHandler: { (nsPersistentStoreDescription, error) in
if let error = error {
fatalError(error.localizedDescription)
}
})
}
static func deleteAndRebuild() {
try! persistentContainer.persistentStoreCoordinator.destroyPersistentStore(at: url, ofType: storeType, options: nil)
loadStores()
}
}
如果需要删除所有对象且不删除备份文件,可以使用以下方法:
- (void)deleteAllObjectsInContext:(NSManagedObjectContext *)context
usingModel:(NSManagedObjectModel *)model
{
NSArray *entities = model.entities;
for (NSEntityDescription *entityDescription in entities) {
[self deleteAllObjectsWithEntityName:entityDescription.name
inContext:context];
}
}
- (void)deleteAllObjectsWithEntityName:(NSString *)entityName
inContext:(NSManagedObjectContext *)context
{
NSFetchRequest *fetchRequest =
[NSFetchRequest fetchRequestWithEntityName:entityName];
fetchRequest.includesPropertyValues = NO;
fetchRequest.includesSubentities = NO;
NSError *error;
NSArray *items = [context executeFetchRequest:fetchRequest error:&error];
for (NSManagedObject *managedObject in items) {
[context deleteObject:managedObject];
NSLog(@"Deleted %@", entityName);
}
}
注意它可能非常慢(取决于对象图中有多少对象)。
我采取了Grouchal的代码,为了加快速度,我使用了并发模式的枚举(NSEnumerationConcurrent),它比for循环快了一点(在我的应用程序中,我为测试人员添加了这个功能,以便他们可以清除数据和做测试用例,而不是删除和安装应用程序)
- (void)resetObjects
{
[self deleteAllObjectsInEntity:@"Entity1"];
[self deleteAllObjectsInEntity:@"Entity2"];
[self deleteAllObjectsInEntity:@"Entity3"];
[self deleteAllObjectsInEntity:@"Entity4"];
}
-(void) deleteAllObjectsInEntity:(NSString*) entityName
{
MainDataContext *coreDataContext = [MainDataContext sharedInstance];
NSManagedObjectContext *currentContext = coreDataContext.managedObjectContext;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:currentContext];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *items = [currentContext executeFetchRequest:fetchRequest error:&error];
[items enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(NSManagedObject * obj, NSUInteger idx, BOOL *stop) {
[currentContext deleteObject:obj];
}];
if (![currentContext save:&error]) {
NSLog(@"Error deleting %@ - error:%@",entityName,error);
}
}