【发布时间】：2015-03-14 10:39:53
【问题描述】：
我有一个包含UITableView 的屏幕，在这个屏幕中我有一个NSManagedObjects 数组。它工作得很好，但是当我尝试移动到另一个屏幕（单击特定单元格，然后推送一个新屏幕），然后返回到同一个 UITableView 屏幕时，所有对象都丢失了。
这是什么意思？我尝试打印NSManagedObjects 的数组，这很好，所有对象都在那里，但是当我打印每个对象的描述时，我从所有对象属性中得到nil。
有人知道是什么原因吗？我不知道为什么，但它在 12 小时前运行良好，但现在一切都搞砸了，我不知道我做了什么。
提前致谢！
保存方法：
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
else {
NSLog(@"Context saved!");
}
}
}
这就是我保存对象的方式：
NSDictionary *response = responseObject;
if ([[response valueForKey:@"status"] rangeOfString:@"ok"].location != NSNotFound)
{
NSArray *data = [response objectForKey:@"data"];
if (data.count != 0)
{
if (page.integerValue == 0) {
[[DownloadData sharedData] deleteAllObjectsFromEntityName:@"DbHomeCuisine"];
[[DownloadData sharedData] deleteAllObjectsFromEntityName:@"DbHomeCategory"];
[[DownloadData sharedData] deleteAllObjectsFromEntityName:@"DbHomeDish"];
}
NSMutableArray *homePageObjects = [[NSMutableArray alloc] initWithCapacity:data.count];
for (NSDictionary *object in data)
{
NSNumber *type = [object objectForKey:@"type"];
switch (type.integerValue) {
case 1:
{
NSDictionary *content = [object objectForKey:@"content"];
NSManagedObjectContext *context = [[MainDb sharedDb] managedObjectContext];
DbHomeCuisine *homeCuisine = [NSEntityDescription insertNewObjectForEntityForName:@"DbHomeCuisine" inManagedObjectContext:context];
NSInteger cuisineId = [[content valueForKey:@"cuisine_id"] integerValue];
homeCuisine.cuisine = [self gCuisineWithCuisineId:[NSNumber numberWithInteger:cuisineId]];
NSInteger count = [[content valueForKey:@"count"] integerValue];
homeCuisine.count = [NSNumber numberWithInteger:count];
homeCuisine.type = type;
[homePageObjects addObject:homeCuisine];
}
break;
case 2:
{
NSDictionary *content = [object objectForKey:@"content"];
NSManagedObjectContext *context = [[MainDb sharedDb] managedObjectContext];
DbHomeCategory *homeCategory = [NSEntityDescription insertNewObjectForEntityForName:@"DbHomeCategory" inManagedObjectContext:context];
NSInteger categoryId = [[content valueForKey:@"category_id"] integerValue];
homeCategory.category = [self gCategoryWithCategoryId:[NSNumber numberWithInteger:categoryId]];
NSInteger count = [[content valueForKey:@"count"] integerValue];
homeCategory.count = [NSNumber numberWithInteger:count];
homeCategory.type = type;
[homePageObjects addObject:homeCategory];
}
break;
case 3:
{
NSDictionary *content = [object objectForKey:@"content"];
NSManagedObjectContext *context = [[MainDb sharedDb] managedObjectContext];
DbHomeDish *homeDish = [NSEntityDescription insertNewObjectForEntityForName:@"DbHomeDish" inManagedObjectContext:context];
homeDish.dishId = [self gInt:content forKey:@"dish_id"];
homeDish.headline = [AppUtils checkForEmptyValue:[content valueForKey:@"title"]];
homeDish.text = [AppUtils checkForEmptyValue:[content valueForKey:@"description"]];
homeDish.cuisineId = [self gInt:content forKey:@"cuisine_id"];
homeDish.cuisine = [self gCuisineWithCuisineId:homeDish.cuisineId];
homeDish.creationDate = [AppUtils checkForEmptyValue:[content valueForKey:@"creation_time"]];
homeDish.userId = [self gInt:content forKey:@"user_id"];
homeDish.longitude = [self gDouble:content forKey:@"lng"];
homeDish.latitude = [self gDouble:content forKey:@"lat"];
homeDish.lastPromoteDate = [AppUtils checkForEmptyValue:[content valueForKey:@"last_promote_time"]];
homeDish.price = [self gInt:content forKey:@"price"];
homeDish.currency = [AppUtils checkForEmptyValue:[content valueForKey:@"currency"]];
homeDish.countryName = [AppUtils checkForEmptyValue:[content valueForKey:@"country_name"]];
homeDish.baseCurrency = [self gFloat:content forKey:@"base_currency"];
homeDish.exchangeRate = [self gFloat:content forKey:@"exchange_rate"];
homeDish.countryIsoCode = [AppUtils checkForEmptyValue:[content valueForKey:@"country_iso_code"]];
homeDish.mainPhoto = [AppUtils checkForEmptyValue:[content valueForKey:@"main_photo"]];
homeDish.like = [self gLikeWithDishId:homeDish.dishId];
homeDish.profileImageURL = [AppUtils checkForEmptyValue:[content valueForKey:@"profile_img_url"]];
homeDish.likeCount = [self gInt:content forKey:@"likes"];
homeDish.type = type;
[homePageObjects addObject:homeDish];
}
break;
default:
break;
}
}
// @@log -- Save data to core data and device
//
//
[[MainDb sharedDb] saveContext];
if (success) {
success(operation, homePageObjects);
}
}
}
【问题讨论】：
-
显示数据模块、保存和 UI 转换的代码
-
@Wain 在我的核心数据模型中有 15 个实体...如何显示它们？保存是基础 CoreData 保存。 UI 的过渡是 UINavigationController 的简单推送。
-
你怎么回来的？我们不需要所有实体，只需要一个关于如何更新和保存模型的示例，然后再次查询它。过渡部分更多的是关于你回到什么。目前，您的问题是一个广泛的“猜测我可能做错了什么”，因为这是无法回答的......
-
@Wain 转换都是普通的 Push 和 Pop 方法。我忘记了另一件重要的事情，当我弹出屏幕并返回 UITableView 并显示 nil 对象时，我得到了与推动控制器之前看到的相同的 3 个对象，当我向下滚动 UITableView 控制器时，我得到了那些3 重新来过。
-
我假设您正在使用
viewDidLoad:方法查询您的数据库？还是类似的？您发布的代码看起来不错：您将什么记录到调试器中？您的托管对象似乎正在被释放。
标签： ios objective-c uitableview core-data nsmanagedobject