如何在Core Data中保存数据？

Question

我创建了一个名为House的实体。该实体有两个属性：street（类型为string）和numOfStories（类型为整数32）。我能够在AppDelegate.m didFinishLaunchingWithOptions方法中成功保存和NSLog数据。但是，当我尝试制作2个文本字段并显示用户的输入，并按下要保存的按钮时，结果是SIGABRT。

以下是我在MainViewController.m中使用的所有代码：

- (BOOL)createNewHouseWithStreet:(NSString *)paramStreet numOfStories:  (NSUInteger)paramNumOfStories
{
BOOL result = NO;

if ([paramStreet length] == 0)
{
    NSLog(@"Street name is mandatory");
    return NO;
}

House *newHouse = [NSEntityDescription insertNewObjectForEntityForName:@"House" inManagedObjectContext:self.managedObjectContext];


if (newHouse == nil)
{
    NSLog(@"Failed to create the new House");
    return NO;
}

newHouse.street = paramStreet;
newHouse.numOfStories = @(paramNumOfStories);

NSError *savingError = nil;

if ([self.managedObjectContext save:&savingError])
{
    return YES;
}

else
{
    NSLog(@"Failed the save the new House. Error = %@", savingError);
}

return result;

}

以下我有

- (IBAction)save:(id)sender {



[self createNewHouseWithStreet:@"10 WYOMING" numOfStories:2];
[self createNewHouseWithStreet:@"6 WYOMING" numOfStories:3];


NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"House"];

NSError *requestError = nil;

NSArray *houses = [self.managedObjectContext executeFetchRequest:fetchRequest error:&requestError];

if ([houses count] > 0)
{
    NSUInteger counter = 1;

    for (House *thisHouse in houses)
    {
        NSLog(@"House %lu Street Name = %@", (unsigned long)counter, thisHouse.street);
        NSLog(@"House %lu number of stories = %ld", (unsigned long)counter, (unsigned long)[thisHouse.numOfStories unsignedIntegerValue]);
        counter++;

    }
}
else
{
    NSLog(@"Could not find any House entities in the context.");
}

}

所以奇怪的是，每当我点击保存按钮时，这个代码最终导致sigabrt，但是当我将save方法中的代码放入我的AppDelegate.m didFinishLaunchingWithOptions方法时，它的效果很好。

感谢所有帮助，谢谢。