Example.m

    [super viewWillAppear:animated];
    NSManagedObjectContext *context = [NSManagedObjectContext MR_contextForCurrentThread];
    
    // ここで、FEUnitはFEClanに対してclanというrelationを持っているとする
    // FEClanはFEUnitに対してunitsというrelationを持っているとする
    // NSManagedObjectIDで検索
    // Property clanID must be permanent since a temporary ID cannot handle this query
    
    self.fetchedResultsController = [FEUnit MR_fetchAllGroupedBy:nil
                                                   withPredicate:[NSPredicate predicateWithFormat:@"clan == %@", self.clanID]
                                                        sortedBy:@"firstName"
                                                       ascending:YES
                                                        delegate:nil
                                                       inContext:context];
    
    NSAssert(self.clanID, @"Property clanID must be set before view will appear.");
    NSAssert(!self.clanID.isTemporaryID, @"Property clanID must be a permanent ID.");
    
    
    // NSManagedObject直指定でもOK、これだとIDがテンポラリだろうがなんだろうが問題ない
    
    self.fetchedResultsController = [FEUnit MR_fetchAllGroupedBy:nil
                                                   withPredicate:[NSPredicate predicateWithFormat:@"clan == %@", self.clan]
                                                        sortedBy:@"firstName"
                                                       ascending:YES
                                                        delegate:nil
                                                       inContext:context];

    // NULL指定も可能なはず

    self.fetchedResultsController = [FEUnit MR_fetchAllGroupedBy:nil
                                                   withPredicate:[NSPredicate predicateWithFormat:@"clan == NULL"]
                                                        sortedBy:@"firstName"
                                                       ascending:YES
                                                        delegate:nil
                                                       inContext:context];

    // 1:Nで逆指定

    self.fetchedResultsController = [FEClan MR_fetchAllGroupedBy:nil
                                                   withPredicate:[NSPredicate predicateWithFormat:@"units in %@", self.someUnits]
                                                        sortedBy:@"name"
                                                       ascending:YES
                                                        delegate:nil
                                                       inContext:context];