看了苹果的文档，里面写的例子：

If you use a to-many relationship, the construction of a predicate is slightly different. If you want to fetch Departments in which at least one of the employees has the first name "Matthew," for instance, you use an ANY operator as shown in the following example:

 NSPredicate *predicate = [NSPredicate predicateWithFormat:
    @"ANY employees.firstName like 'Matthew'"];

所以，我觉得查询应该是：

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(name = %@) AND (ANY aObjects.count > 10)", @"hello"];

脑补的，没测试。。。不好用请更正我

NSEntityDescription *entity = [NSEntityDescription
                                   entityForName:@"ClassB"
                                   inManagedObjectContext:context];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:entity];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(name = %@) AND (aObjects.count > 10)", @"hello"];
[fetchRequest setPredicate:predicate];