保存核心數據對象時出錯

Question

我對保存對象時收到的一個錯誤感到非常困惑。我收到以下錯誤（當我打印出詳細說明時）：

2015-05-08 08:19:51.589 Br[11240:208443] Core Data Save Error 

          NSValidationErrorKey 
activityObject 

          NSValidationErrorPredicate 
(null) 

          NSValidationErrorObject 
<BRActivity: 0x7deb2aa0> (entity: BRActivity; id: 0x7deb2780 <x-coredata:///BRActivity/t86C0E8CD-2B6C-4AF7-986A-4797B7BEFDF5> ; data: { 
activities =  (
); 
activityObject = nil; 
activityType = 0; 
body = "Someone left a comment on your post."; 
timestamp = "2015-05-08 04:24:46 +0000"; 
uuidString = "c6a06b45-e2d5-45bd-9f64-20b13ac87526"; 
}) 

          NSLocalizedDescription 
The operation couldn’t be completed. (Cocoa error 1570.) 
2015-05-08 08:19:51.590 Br[11240:208443] Core Data Save Error 

因此從互聯網上看，這似乎是一個關係問題。所以一個Br職位有一個叫做活動關係的關係，其中的倒數是一個活動對象。現在，從錯誤中我們可以看出，它是零。那麼我們在這裏看到了什麼樣的解決方案......有沒有辦法讓關係成爲「可選」（好吧，無！）或者我應該添加一個活動對象？我真的不想在這裏破壞任何東西，所以如果有一個微妙的解決方案讓我知道。感謝一堆傢伙！

而且，這裏是周邊的保存方法：

- (void)importArray:(NSArray *)array entityName:(NSString *)entityName attributeName:attributeName error:(NSError *__autoreleasing *)error { 
NSParameterAssert(array); 
NSParameterAssert(entityName); 

[self.context performBlockAndWait:^{ 
    for (NSDictionary *jsonDictionary in array) { 
     NSManagedObject *managedObject = [NSManagedObject upsertWithContext:self.context entityName:entityName dictionary:jsonDictionary attributeName:attributeName error:error]; 
     if (nil == managedObject) { 
      if ([self.context hasChanges]) { 
       [self.context rollback]; 
      } 
      return; 
     } 
    } 

    if ([self.context hasChanges]) { 
     if (![self.context save:error]) { 
      NSError *err = *error; 


      NSDictionary *userInfo = [err userInfo]; 
      if ([userInfo valueForKey:@"NSDetailedErrors"] != nil) { 
       // ...and loop through the array, if so. 
       NSArray *errors = [userInfo valueForKey:@"NSDetailedErrors"]; 
       for (NSError *anError in errors) { 

        NSDictionary *subUserInfo = [anError userInfo]; 
        subUserInfo = [anError userInfo]; 
        // Granted, this indents the NSValidation keys rather a lot 
        // ...but it's a small loss to keep the code more readable. 
        NSLog(@"Core Data Save Error\n\n \ 
          NSValidationErrorKey\n%@\n\n \ 
          NSValidationErrorPredicate\n%@\n\n \ 
          NSValidationErrorObject\n%@\n\n \ 
          NSLocalizedDescription\n%@", 
          [subUserInfo valueForKey:@"NSValidationErrorKey"], 
          [subUserInfo valueForKey:@"NSValidationErrorPredicate"], 
          [subUserInfo valueForKey:@"NSValidationErrorObject"], 
          [subUserInfo valueForKey:@"NSLocalizedDescription"]); 
       } 
      } 


      NSLog(@"Error: %@", err.localizedDescription); 
     } 
     return; 
    } 
}]; 
} 

Answer 1

是的，關係可以是可選的。選擇關係，您將在右上角的數據檢查器窗格中看到可選的可選項。