ios - 如何使用 NSPredicate 从 CoreData 中删除选定数量的行？

Question

我想从 CoreData 表中删除选定的项目列表:一些具有特定 namesToDelete 的人:

NSError*        error        = nil;
NSFetchRequest* request      = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:@"Person"
                               inManagedObjectContext:managedObjectContext]];
NSPredicate*    predicate    = [NSPredicate predicateWithFormat:@"NOT (name IN %@)", namesToDelete];
[request setPredicate:predicate];
NSArray*         deleteArray = [managedObjectContext executeFetchRequest:request error:&error];
if (error == nil)
{
    for (NSManagedObject* object in deleteArray)
    {
        [managedObjectContext deleteObject:object];
    }

    [managedObjectContext save:&error];
    //### Error handling.
}
else
{
    //### Error handling.
}

这可行，但这是在 CoreData 中执行此操作的最简单/最短的方法吗？

Answer 1

关于最好的修剪是这样的:

NSError*        error        = nil;
NSFetchRequest* request      = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
[request setPredicate:[NSPredicate predicateWithFormat:@"NOT (name IN %@)", namesToDelete]];
NSArray*         deleteArray = [managedObjectContext executeFetchRequest:request error:&error];

if (deleteArray != nil)
{
    for (NSManagedObject* object in deleteArray)
    {
        [managedObjectContext deleteObject:object];
    }

    [managedObjectContext save:&error];
    //### Error handling.
}
else
{
    //### Error handling.
}

另请注意，您检查数组是否作为成功标准返回，而不是检查 nil 中的错误。同样，对于 save:，您应该检查返回的 BOOL。