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
iOS 10和Swift 3
假设您的实体名称是“Photo”,并且您创建了一个CoreDataStack类…
func clearData() {
do {
let context = CoreDataStack.sharedInstance.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Photo")
do {
let objects = try context.fetch(fetchRequest) as? [NSManagedObject]
_ = objects.map{$0.map{context.delete($0)}}
CoreDataStack.sharedInstance.saveContext()
} catch let error {
print("ERROR DELETING : \(error)")
}
}
}
这里有一个很好的教程,教你如何使用CoreData以及如何使用这个方法。 https://medium.com/compileswift/parsing-json-response-and-save-it-in-coredata-step-by-step-fb58fc6ce16f#.1tu6kt8qb
其他回答
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()
}
}
龙道9+ Swift 2
删除所有实体中的所有对象
func clearCoreDataStore() {
let entities = managedObjectModel.entities
for entity in entities {
let fetchRequest = NSFetchRequest(entityName: entity.name!)
let deleteReqest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try context.executeRequest(deleteReqest)
} catch {
print(error)
}
}
}
适用于所有版本。传递实体名称并遍历删除所有条目并保存上下文。
func deleteData(entityToFetch: String, completion: @escaping(_ returned: Bool) ->()) {
var context = NSManagedObjectContext()
if #available(iOS 10.0, *) {
context = self.persistentContainer.viewContext
} else {
context = self.managedObjectContext
}
let fetchRequest = NSFetchRequest<NSFetchRequestResult>()
fetchRequest.entity = NSEntityDescription.entity(forEntityName: entityToFetch, in: context)
fetchRequest.includesPropertyValues = false
do {
let results = try context.fetch(fetchRequest) as! [NSManagedObject]
for result in results {
context.delete(result)
}
try context.save()
completion(true)
} catch {
completion(false)
print("fetch error -\(error.localizedDescription)")
}
}
作为一个快速参考,以节省在其他地方搜索-删除后重新创建持久存储可以用:
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// do something with the error
}
使用这个
+(NSArray *)fetchDataFromEntity:(NSString *)entityName context:(NSManagedObjectContext *)context
{
NSFetchRequest * fetchRequest =[[NSFetchRequest alloc] init];
NSEntityDescription * CategoriesEntity = [NSEntityDescription entityForName:entityName inManagedObjectContext:context];
[fetchRequest setEntity:CategoriesEntity];
NSError * error;
NSInteger count = [context countForFetchRequest:fetchRequest error:&error];
if (count && count>0) {
NSArray * fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects && fetchedObjects.count>0) {
return fetchedObjects;
}else
return nil;
}
else
return nil;
}
+ (void)deleteObjectsOfArray:(NSMutableArray*)ary context:(NSManagedObjectContext *)context {
for (NSManagedObject * obj in ary) {
[context deleteObject:obj];
}
NSError *saveError = nil;
[context save:&saveError];
}
+ (void)deleteEntity:(NSString *)entityName context:(NSManagedObjectContext *)context {
NSArray *listArray = [self fetchDataFromEntity:entityName context:context];
[self deleteObjectsOfArray:[NSMutableArray arrayWithArray:listArray] context:context];
}