Core Data 不会触发实体属性的错误，但会触发关系

Posted 2023-03-03

【中文标题】Core Data 不会触发实体属性的错误，但会触发关系

【英文标题】：Core Data not firing fault for entity properties but does for relationships

【发布时间】：2016-03-01 18:57:23

【问题描述】：

我有一个名为 Trigger 的核心数据实体，它与另一个名为 ActiveTrigger 的实体具有多对一的关系。当我使用[request setReturnsObjectsAsFaults:NO]; 查询触发器对象的核心数据时，查询结果在每个触发器上都有一个 ActiveTrigger 实体的 NSSet，即 trigger.activeTriggers。然而，ActiveTrigger 对象有一个数据错误，当我访问任何属性时不会触发该错误，但当我访问 ActiveTrigger 上的关系之一时会触发。访问属性或关系时不应该触发故障吗？使用关系触发故障后，未触发故障返回后返回的相同属性（null）为实际值。

NSFetchRequest * request = [NSFetchRequest fetchRequestWithEntityName:NSStringFromClass([Trigger class])];
[request setPredicate:[NSPredicate predicateWithFormat:@"identifier IN %@", triggerIds]];
[request setReturnsObjectsAsFaults:NO];

NSError * error = nil;
NSArray * results = [[NSManagedObjectContext sharedManagedObjectContext] executeFetchRequest:request error:&error];
for (Trigger * trigger in results) 
    for (ActiveTrigger * activeTrigger in trigger.activeTriggers) 
        NSLog(@"Here is the survey name as a property on the ActiveTrigger 1:  %@", activeTrigger.surveyName);
        NSLog(@"Here is the survey name via the relationship:                  %@", activeTrigger.survey.name);
        NSLog(@"Here is the survey name as a property on the ActiveTrigger 2:  %@", activeTrigger.surveyName);
    



//Here are the logs resulting from the code above
2016-03-01 13:48:28.809 AppName[31787:1480404] Here is the survey name as a property on the ActiveTrigger 1:  (null)
2016-03-01 13:48:28.811 AppName[31787:1480404] Here is the survey name via the relationship:                  All Q
2016-03-01 13:48:28.811 AppName[31787:1480404] Here is the survey name as a property on the ActiveTrigger 2:  All Q

第一个日志后的断点确认activeTrigger对象在尝试访问surveyName属性后仍有数据故障

【参考方案1】：

解决了。事实证明，ActiveTrigger 实现中的属性使用@synthesize 而不是@dynamic。更改为动态，访问属性时正确触发数据错误