当最小iOS为9.0时，使用NSBatchDeleteRequest删除多条记录。如果是后台线程，执行NSManagedObjectContext save，否则使用NSFetchRequest获取记录并删除for循环中的所有记录，删除完成后保存。

Dave Delongs的Swift 2.0回答让我崩溃了(在iOS 9中)

但这个方法奏效了:

let fetchRequest = NSFetchRequest(entityName: "Car")
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)

    do {
        try managedObjectContext.executeRequest(deleteRequest)
        try managedObjectContext.save()
    }
    catch let error as NSError {
       // Handle error
    }

如果实体包含很多条目，最好的方法是这样，因为它节省内存

 - (void)deleteAll:(NSManagedObjectContext *)managedObjectContext entityName:(NSString *)entityName
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    [managedObjectContext setUndoManager:nil];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext];
    [fetchRequest setEntity:entity];
    [fetchRequest setIncludesPropertyValues:NO];
    [fetchRequest setFetchLimit:100]; // you can change this number if you want
    NSError *error;
    NSArray *items = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
    while ([items count] > 0) {
        @autoreleasepool {
            for (NSManagedObject *item in items) {
                [managedObjectContext deleteObject:item];
            }
            if (![managedObjectContext save:&error]) {
                NSLog(@"Error deleting %@ - error:%@",self.entityName, error);
            }
        }
        items = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
    }
}

iOS 11.3和Swift 4.1

let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest )
        batchDeleteRequest.resultType = .resultTypeCount
        do {
            let batchDeleteResult = try dataController.viewContext.execute(batchDeleteRequest) as! NSBatchDeleteResult
            print("The batch delete request has deleted \(batchDeleteResult.result!) records.")
            dataController.viewContext.reset() // reset managed object context (need it for working)
        } catch {
            let updateError = error as NSError
            print("\(updateError), \(updateError.userInfo)")
        }

你必须在执行之后调用重置。如果不是，它将不会在表视图上更新。

Swift 3解决方案与iOS 9 'NSBatchDeleteRequest'和回退到早期的iOS版本，作为'NSManagedObjectContext'的扩展实现。苹果参考https://developer.apple.com/library/content/featuredarticles/CoreData_Batch_Guide/BatchDeletes/BatchDeletes.html

extension NSManagedObjectContext {
    func batchDeleteEntities<T: NSManagedObject>(ofType type: T.Type) throws {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: String(describing: type.self))
        if #available(iOS 9.0, *) {
            let request = NSBatchDeleteRequest(fetchRequest: fetchRequest)
            let result = try execute(request) as? NSBatchDeleteResult
            if let objectIDArray = result?.result as? [NSManagedObjectID] {
                let changes = [NSDeletedObjectsKey: objectIDArray]
                NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [self])
            }
        } else {
            fetchRequest.includesPropertyValues = false
            let results = try fetch(fetchRequest)
            if let actualResults = results as? [NSManagedObject], !actualResults.isEmpty {
                actualResults.forEach { delete($0) }
            }
        }
    }
}

更干净和通用一点:添加这个方法:

- (void)deleteAllEntities:(NSString *)nameEntity
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:nameEntity];
    [fetchRequest setIncludesPropertyValues:NO]; //only fetch the managedObjectID

    NSError *error;
    NSArray *fetchedObjects = [theContext executeFetchRequest:fetchRequest error:&error];
    for (NSManagedObject *object in fetchedObjects)
    {
        [theContext deleteObject:object];
    }

    error = nil;
    [theContext save:&error];
}