免责声明：我是一个完整的 CoreData 菜鸟。我在装有 iOS 6.0.1 的 iPhone 4S 上运行我的应用程序。
背景
我的应用程序的一部分使用 a 获取图像UIImagePicker并使用 CoreData 将它们保存到磁盘。所述图像与模型中的活动相关联。活动与图像具有一对多的关系。
我需要在捕获后立即将图像保存到磁盘，然后将它们排除在内存之外，保留缩略图以供显示。如果我不这样做，iOS 将在捕获相对较少数量的图像后杀死我的应用程序使用太多内存。
我将缩略图作为一个单独的实体，以避免在我只需要缩略图的情况下将整个图像放入内存。缩略图与图像具有一对一的关系。此外，由于各种原因，我没有使用 Core Data 来存储缩略图数据；相反，我存储文件名，并自己管理磁盘上的文件。
所有这一切意味着，如果用户在添加了至少一个 Image 之后取消添加 Activity，那么用户添加的 Images 和 Thumbnails 都需要删除。
问题
当我尝试删除添加的图像对象时，会发生两件事。首先，Core Data 抱怨我的删除规则：
Core Data: annotation: repairing missing delete propagation for to-one relationship image on object <Thumbnail: 0x1dd4d9e0> (entity: Thumbnail; id: 0x1dd4d410 <x-coredata:///Thumbnail/tE7E99D89-C986-4287-ABBD-C6BA7006E9264> ; data: {
activity = nil;
fileName = "ECD70C72-745A-4959-BF41-586E9521F1D6";
image = "0x1dd9f960 <x-coredata:///Image/tE7E99D89-C986-4287-ABBD-C6BA7006E9263>";
}) with bad fault 0x1dd9f960 <x-coredata:///Image/tE7E99D89-C986-4287-ABBD-C6BA7006E9263>
其次，当我尝试保存托管对象上下文时，保存失败，Core Data 抛出异常。这是 NSError 对象的输出：
Error Domain=NSCocoaErrorDomain Code=134030 "The operation couldn’t be completed. (Cocoa error 134030.)"
UserInfo=0x1f0ca270 {NSAffectedObjectsErrorKey=(
"<Image: 0x1dd9f910> (entity: Image; id: 0x1dd9f960 <x-coredata:///Image/tE7E99D89-C986-4287-ABBD-C6BA7006E9263> ;
data: {
activity = nil;
image = nil;
thumbnail = nil;
})"
), NSUnderlyingException=Cannot delete object that was never inserted.}
所以。显然我正在尝试删除我从未插入的对象？只有我很确定我做到了。
关系详情
活动 <1-*> 图像；删除规则：cascade
--> Inverse：Image <1-1> Activity；删除规则：无效
图像 <1-1> 缩略图；删除规则：级联
-->逆：缩略图<1-1>图片；删除规则：无效
相关代码
图像采集：
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage* acquiredImage = (UIImage*)info[UIImagePickerControllerEditedImage];
if (!acquiredImage) {
acquiredImage = (UIImage*)info[UIImagePickerControllerOriginalImage];
}
// Save the image to disk so we can fault it and free up its memory
NSManagedObjectContext* moc = [(ATAppDelegate*)[[UIApplication sharedApplication] delegate] managedObjectContext];
Image* imageToSave = [NSEntityDescription insertNewObjectForEntityForName:@"Image" inManagedObjectContext:moc];
Thumbnail* thumbToSave = [NSEntityDescription insertNewObjectForEntityForName:@"Thumbnail" inManagedObjectContext:moc];
[addedImageManagedObjects addObject:imageToSave];
[addedThumbnailManagedObjects addObject:thumbToSave];
[thumbToSave setThumbnailImage:acquiredImage];
imageToSave.thumbnail = thumbToSave;
NSError* error;
[moc save:&error];
// TODO: error handling
// I know it doesn't look it, but this call will turn the imageToSave into a fault, thus freeing up its memory
[moc refreshObject:imageToSave mergeChanges:NO];
// NOW, we can add the thumbnail image to our collection view
// NOTE, -thumbnailImage is a method on my Thumbnail NSManagedObject subclass
[self addImage:[thumbToSave thumbnailImage] toCollectionView:imageDisplayView];
[self dismissModalViewControllerAnimated:YES];
}
取消处理程序：
- (IBAction)cancel:(id)sender {
NSManagedObjectContext* moc = [(ATAppDelegate*)[[UIApplication sharedApplication] delegate] managedObjectContext];
// Delete any images we saved to disk
// Note that the activity object's changes get discarded b/c they were made on the child managed object context
// (We couldn't do that for images b/c we needed them to be written to disk and then faulted out of memory)
for (Thumbnail* thumb in addedThumbnailManagedObjects) {
// This method deletes the thumbnail image file whose storage I am managing myself
[thumb deleteThumbnailFile];
// I shouldn't have to explicitly delete the thumbnail since the delete of its image should cascade down...right?
}
for (Image* image in addedImageManagedObjects) {
[moc deleteObject:image];
}
NSError* error;
if (![moc save:&error]) {
NSLog(@"%@", error);
}
// TODO: error handling
[self resetToPristineState];
[self.presentingViewController dismissModalViewControllerAnimated:YES];
}
概括
我看不出哪里出错了，我收到的错误消息也没有帮助。更糟糕的是，谷歌搜索错误消息并没有给我任何有用的结果。因此，我向各位经验丰富的优秀人士寻求帮助。