Question

我有以下代码，目前清除我的NSManagedObjectContext中的所有对象：

- (void)clearObjectList:(NSString *)identifier
{
    // TODO: Delete any entries with the identifier at the start of the object's name
    NSLog(@"Clearing the URL list...");

    NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
    NSFetchRequest * fetch = [[NSFetchRequest alloc] init];
    [fetch setEntity:[NSEntityDescription entityForName:@"URL" inManagedObjectContext:context]];
    NSArray * result = [context executeFetchRequest:fetch error:nil];
    for (id basket in result)
    {
        // Code here to check if we should delete this object
        [context deleteObject:basket];
    }

    NSError *error = nil;
    if (![context save:&error]) {
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        //abort();
    }
}

我对URL的数据模型是：

dateAccessed: Date
        name: String
         url: String

我想访问对象键name以确定是否应将其删除。我该如何访问？

Answer 1

试试这个：

for(URL *basket in result)
{
    if([basket.name isEqualToString:identifier])
        [context deleteObject:basket];
}

Answer 2

在循环搜索结果时，您知道您将获得的所有内容都是NSManagedObject。或者，如果您已创建NSManagedObject子类，则只会返回URL个对象。因此，您可以在for循环中将id替换为NSManagedObject *或URL *。

如果您确实创建了我建议的子类，则可以使用点表示法name访问basket.name。如果您没有，可以通过拨打[basket valueForKey:@"name"]来访问它。

如何清除NSManagedObjectContext中的选定对象

2 个答案: