setupFetchedResultsController中的特殊結果

+-----------+   +-----------+ 
    | -Parada- |   | -Autobus- | 
    +-----------+   +-----------+ 
    | nombre |   | circuito | 
    +-------------+   +-------------+ 
    |Relationships|   |Relationships| 
    +-------------+   +-------------+ 
    | byParada |<--------> | parada | 
    +-----------+   +-----------+

我試圖根據circuitos之間的關係來獲取Paradas列表。setupFetchedResultsController中的特殊結果

對於防爆：

Autobus 1 has Circuito=1 and Parada=Town 
Autobus 2 has Circuito=2 and Parada=City 
Autobus 3 has Circuito=3 and Parada=Coast 
Autobus 4 has Circuito=4 and Parada=Park

所以我試圖讓具有來自定義具有較高的電路帕拉達斯的列表，這是不容易解釋，但在我的應用程序，你有兩個選擇器具有相同Parada的列表，取決於您在第一個選取器中選擇的Parada，第二個將只顯示具有更高Circuito的Parada。

例如，如果您在第一個選擇器中選擇了「城市」，則第二個選擇器將讓您選擇「海岸」或「公園」。

這裏是我試圖修復代碼：

- (void)setupFetchedResultsController 
{ 
    // 0 - Ensure you have a MOC 
    if (!self.managedObjectContext) { 
     NSLog(@"RolePickerTVCell wasn't given a Managed Object Context ... so it's going to go get one itself!"); 
     RCAppDelegate *ad = [[UIApplication sharedApplication] delegate]; 
     self.managedObjectContext = ad.managedObjectContext; 
    } 

    // 1 - Decide what Entity you want 
    NSString *entityName = @"Parada"; // Put your entity name here 
    NSLog(@"RolePickerTVCell is Setting up a Fetched Results Controller for the Entity named %@", entityName); 

    // 2 - Request that Entity 
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:entityName]; 

    // 3 - Filter it if you want 
    // Here's the problem: 

    NSString *predString = [NSString stringWithFormat:@"ANY byParada.circuito > '%@'", self.fetchedResultsController]; 
    request.predicate = [NSPredicate predicateWithFormat:predString]; 

    // It shows nothing... 
    NSLog(@"list of Paradas: %@", self.fetchedResultsController); 



    // 4 - Sort it if you want 
    request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"nombre" 
                        ascending:YES 
                         selector:@selector(localizedCaseInsensitiveCompare:)]]; 
    // 5 - Fetch it 
    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request 
                     managedObjectContext:self.managedObjectContext 
                      sectionNameKeyPath:nil 
                        cacheName:nil]; 
    [self.fetchedResultsController performFetch:nil]; 

    NSLog(@"The following roles were fetched for the Picker by ORIGENPickerTVCell:"); 
    for (Parada *fetchedOrigen in [self.fetchedResultsController fetchedObjects]) { 
     NSLog(@"List of Paradas: %@", fetchedOrigen.nombre); 
    } 


}

來源

2014-03-27 Rodrigo

你的斷言設置是錯誤的。
格式化應該發生在謂語結構層次：

request.predicate = [NSPredicate predicateWithFormat:@"byParada.circuito > %@",currentCircuitoAsNSNumber];

哪裏currentCircuitoAsNSNumber是當前選定的「CIRCUITO」，併爲NSNumber類型。

來源

2014-03-27 19:05:51

問題是currentCircuitoAsNSNumber必須是自動的，如果我只知道nombre，我怎麼能得到？ – Rodrigo

你解釋過你選擇了「城市」，這意味着你可以訪問：'相關'Autobus'對象的'byParada.cicuito'，或者你可能給出了你的數據模型的錯誤表示... –

我可以只選擇Parada，但我不知道如何將Parada（Town，City ...）的名稱轉換爲當前的CircuitoAsNSNumber，然後我可以取回它。 – Rodrigo

setupFetchedResultsController中的特殊結果

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