xcode 删除对象 Coredata
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Delete object Coredata
提问by James Dunay
I have a project that uses coredata and i am attmepting to delete from what i have stored. But i keep getting this error.
我有一个使用 coredata 的项目，我想从我存储的内容中删除。但我不断收到此错误。
An NSManagedObjectContext cannot delete objects in other contexts.
I looked at what apple had to say and from what i can tell i have it correct, but something is still off. Any suggestions? Thx!
我查看了苹果要说的内容，从我可以说的内容来看，我是正确的，但仍有一些问题。有什么建议？谢谢！
for (UserNumber *info in pinNumberArray) {
NSSet *time = [[NSSet alloc] initWithSet:info.Times];
for (ErgTimes *ergTimes in time){
NSMutableArray *temp = [[NSMutableArray alloc] initWithObjects:ergTimes.Twok, nil];
NSManagedObject *eventToDelete = [temp objectAtIndex:0];
[managedObjectContext deleteObject:eventToDelete];
}
}
回答by Daniel Thorpe
Well, it's possibly that you've got your objects, context and threads mixed up. NSManagedObjectContextisn't thread safe. To delete an object from a context, you need to have fetched the object "into" the context first, and I guess your managed object was fetched by a different MOC. Without seeing more code I can't tell.
嗯，很可能你把你的对象、上下文和线程搞混了。NSManagedObjectContext不是线程安全的。要从上下文中删除对象，您需要先将对象“提取到”上下文中，我猜您的托管对象是由不同的 MOC 提取的。没有看到更多代码，我无法判断。
However, there is a relatively easy fix. In your for loop, do this instead
但是，有一个相对容易的修复方法。在您的 for 循环中，改为执行此操作
for (ErgTimes *ergTimes in time){
NSMutableArray *temp = [[NSMutableArray alloc] initWithObjects:ergTimes.Twok, nil];
NSManagedObject *eventToDelete = [managedObjectContext objectWithID:[[temp objectAtIndex:0] objectID]];
[managedObjectContext deleteObject:eventToDelete];
}
What this does is get the object in the MOC your currently using using its objectID which is thread-safe.
这样做是使用线程安全的 objectID 获取当前使用的 MOC 中的对象。
回答by Massimo Cafaro
You must use the same NSManagedObjectContextyou used to fetch the objects to delete them. Easiest solution: use the managedObjectContext associated to each object to delete it. Like this:
您必须使用与NSManagedObjectContext获取对象相同的方法来删除它们。最简单的解决方案：使用与每个对象关联的 managedObjectContext 来删除它。像这样：
for (UserNumber *info in pinNumberArray) {
NSSet *time = [[NSSet alloc] initWithSet:info.Times];
for (ErgTimes *ergTimes in time){
NSMutableArray *temp = [[NSMutableArray alloc] initWithObjects:ergTimes.Twok, nil];
NSManagedObject *eventToDelete = [temp objectAtIndex:0];
[eventToDelete.managedObjectContext deleteObject:eventToDelete];
}
}
