Ios MagicalRecord Find（All）有时无法从关系中查找对象

当我关闭模拟器并重新打开它或按下并弹出一些视图控制器时，关系中的对象就消失了。当我第一次将对象保存到核心数据时，仍然可以获取对象

这是将对象保存到核心数据的代码：

for (NSDictionary *obj in results) {
    Stock *stock = [Stock MR_createEntity];
    stock.name = obj[@"name"];
    NSArray *categories = obj[@"categories"];
    if ([categories count] > 0) {
        for (NSDictionary *category in categories) {
            StockCategory *stockCategory = [StockCategory MR_createEntity];
            stockCategory.categoryId = category[@"_id"];
            stockCategory.name = category[@"name"];
            [stock addCategoriesObject:stockCategory];
        }
    }
}
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreWithCompletion:^(BOOL success, NSError *error) {
    self.stocks = [Stock MR_findAllSortedBy:@"createdDate" ascending:NO];
    dispatch_async(dispatch_get_main_queue(), ^{
        [SVProgressHUD dismiss];
        [self.tableView reloadData];
    });
}];

self.stocks = [Stock MR_findAllSortedBy:@"createdDate" ascending:NO];
dispatch_async(dispatch_get_main_queue(), ^{
    [SVProgressHUD dismiss];
    [self.tableView reloadData];
});

以下代码用于从核心数据检索对象：

for (NSDictionary *obj in results) {
    Stock *stock = [Stock MR_createEntity];
    stock.name = obj[@"name"];
    NSArray *categories = obj[@"categories"];
    if ([categories count] > 0) {
        for (NSDictionary *category in categories) {
            StockCategory *stockCategory = [StockCategory MR_createEntity];
            stockCategory.categoryId = category[@"_id"];
            stockCategory.name = category[@"name"];
            [stock addCategoriesObject:stockCategory];
        }
    }
}
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreWithCompletion:^(BOOL success, NSError *error) {
    self.stocks = [Stock MR_findAllSortedBy:@"createdDate" ascending:NO];
    dispatch_async(dispatch_get_main_queue(), ^{
        [SVProgressHUD dismiss];
        [self.tableView reloadData];
    });
}];

self.stocks = [Stock MR_findAllSortedBy:@"createdDate" ascending:NO];
dispatch_async(dispatch_get_main_queue(), ^{
    [SVProgressHUD dismiss];
    [self.tableView reloadData];
});

如果我关闭模拟器并重新启动它，我会从核心数据中获取对象，但股票的StockCategory数组是空的。我记得当我第一次将股票保存到核心数据时，股票的StockCategory数组不是空的。为什么当我重新启动模拟器时，关系中的对象就消失了

模型： 股票

股票类别.h

@class Stock;

@interface StockCategory : NSManagedObject

@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) Stock *stock;

@end

---

您的模型中是否从一开始就有类别？您是否尝试过清理/卸载/重新安装应用程序？当您更改CoreData中的某些内容时，如果您对xcdatamodel进行了一些更改，则可能需要进行一些清理。MR_的完成块是否在退出之前使用completion:get run保存到PersistentStore？这听起来像是一种异步方法。