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)
    }
}

迅速的解决方案:

class func deleteAllManagedObjects() {

        let modelURL = NSBundle.mainBundle().URLForResource("some string", withExtension: "mom")
        let mom = NSManagedObjectModel(contentsOfURL: modelURL)

        for entityName in mom.entitiesByName.keys {
            let fr = NSFetchRequest(entityName: entityName as String)
            let a = Utility.managedObjectContext().executeFetchRequest(fr, error: nil) as [NSManagedObject]
            for mo in a {
                Utility.managedObjectContext().deleteObject(mo)
            }
        }

        Utility.managedObjectContext().save(nil)
    }

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

下面这个版本可以删除每个表中的每条记录。

斯威夫特4

static func resetDatabase() {
    do {
        try dataStore.persistentStoreCoordinator.managedObjectModel.entities.forEach { (entity) in
            if let name = entity.name {
                let fetch = NSFetchRequest<NSFetchRequestResult>(entityName: name)
                let request = NSBatchDeleteRequest(fetchRequest: fetch)
                try mainContext.execute(request)
            }
        }

        try mainContext.save()
    } catch {
        print("error resenting the database: \(error.localizedDescription)")
    }
}

你可以删除SQLite文件-但我选择通过一个函数单独清除表来做到这一点:

- (void) deleteAllObjects: (NSString *) entityDescription  {
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityDescription inManagedObjectContext:_managedObjectContext];
    [fetchRequest setEntity:entity];

    NSError *error;
    NSArray *items = [_managedObjectContext executeFetchRequest:fetchRequest error:&error];
    [fetchRequest release];


    for (NSManagedObject *managedObject in items) {
        [_managedObjectContext deleteObject:managedObject];
        DLog(@"%@ object deleted",entityDescription);
    }
    if (![_managedObjectContext save:&error]) {
        DLog(@"Error deleting %@ - error:%@",entityDescription,error);
    }

}

我选择逐表执行的原因是，它使我在编程时确认删除表的内容是合理的，并且没有我宁愿保留的数据。

这样做会比仅仅删除文件慢得多，如果我这个方法花费太长时间，我将更改为文件删除。

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()
    }
}