在Swift 3中重置实体:

func resetAllRecords(in entity : String) // entity = Your_Entity_Name
    {

        let context = ( UIApplication.shared.delegate as! AppDelegate ).persistentContainer.viewContext
        let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
        let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)
        do
        {
            try context.execute(deleteRequest)
            try context.save()
        }
        catch
        {
            print ("There was an error")
        }
    }

这是一个类似的问题，有人建议设置一个关系删除规则，这样你只需要删除一个对象。因此，如果您已经或可以创建一个与汽车具有多对关系的实体，并将删除规则设置为级联，当您删除更高的实体时，所有的汽车也将被删除。这可以节省一些处理时间，因为您不必执行加载所有汽车的步骤。在更大的数据集中，这可能是绝对必要的。

iOS 10及以上版本

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) ->()) {
        let context = NSManagedObjectContext()
        context = your 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)")
        }
    }

iOS 9及以上版本:

iOS 9添加了一个名为NSBatchDeleteRequest的新类，允许您轻松删除匹配谓词的对象，而无需将它们全部加载到内存中。下面是你如何使用它:

斯威夫特5

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

do {
    try myPersistentStoreCoordinator.execute(deleteRequest, with: myContext)
} catch let error as NSError {
    // TODO: handle the error
}

objective - c

NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Car"];
NSBatchDeleteRequest *delete = [[NSBatchDeleteRequest alloc] initWithFetchRequest:request];

NSError *deleteError = nil;
[myPersistentStoreCoordinator executeRequest:delete withContext:myContext error:&deleteError];

关于批量删除的更多信息可以在WWDC 2015的“Core Data新内容”会议中找到(开始时间约为14:10)。

iOS 8及更早版本:

获取并删除它们:

NSFetchRequest *allCars = [[NSFetchRequest alloc] init];
[allCars setEntity:[NSEntityDescription entityForName:@"Car" inManagedObjectContext:myContext]];
[allCars setIncludesPropertyValues:NO]; //only fetch the managedObjectID

NSError *error = nil;
NSArray *cars = [myContext executeFetchRequest:allCars error:&error];
[allCars release];
//error handling goes here
for (NSManagedObject *car in cars) {
  [myContext deleteObject:car];
}
NSError *saveError = nil;
[myContext save:&saveError];
//more error handling here

延续戴夫·德隆的回答。

Swift版本，照顾iOS 9和以前的版本以及。我还介绍了错误处理:

let appDelegate： AppDelegate = UIApplication.sharedApplication（）.delegate as！应用委托

    let fetchRequest = NSFetchRequest(entityName: "Car")
    if #available(iOS 9.0, *) {
        let delete = NSBatchDeleteRequest(fetchRequest: fetchRequest)
        do {
            try appDelegate.persistentStoreCoordinator.executeRequest(delete, withContext: appDelegate.managedObjectContext)
        } catch let error as NSError {
            print("Error occured while deleting: \(error)")
        }
    } else {
        // Fallback on earlier versions
        let carRequest = NSFetchRequest()
        carRequest.entity = NSEntityDescription.entityForName("Cars", inManagedObjectContext: appDelegate.managedObjectContext)
        carRequest.includesPropertyValues = false

        do {
            let cars: NSArray = try appDelegate.managedObjectContext.executeFetchRequest(carRequest)

            for car in cars {
                appDelegate.managedObjectContext.delete(car)
            }

            try appDelegate.managedObjectContext.save()

        } catch let error as NSError {
            print("Error occured while fetching or saving: \(error)")
        }
    }

快速清除DB中的所有对象:

func purgeAllData() {
    let uniqueNames = persistentContainer.managedObjectModel.entities.compactMap({ $0.name })

    uniqueNames.forEach { (name) in
      let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: name)
       let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
         do {
        try persistentContainer.viewContext.execute(batchDeleteRequest)
      } catch {
        let nserror = error as NSError
        fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
      }
   }
 }