Question

我正在尝试在应用程序从Web服务器获得响应时更新我的本地数据库。当应用程序从Web服务器获取更新时，我通过将id与响应匹配来获取本地数据库中的数据，并获取一行并执行更新代码，但本地数据库不会更新，也不会出错。应该是什么解决方案???

-(void)checkID:(NSMutableDictionary *)dict
{
    NSDictionary *dictEvent = [dict objectForKey:@"Event"];

    NSManagedObjectContext *context = [self managedObjectContext];

    NSManagedObject *selectedManagedObject = nil;

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Events" inManagedObjectContext:context];
    NSSortDescriptor *sortDescObj = [[NSSortDescriptor alloc] initWithKey:@"event_id" ascending:YES];
    NSError *error = nil;

    NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"user_id=%@ and event_id=%@",[NSNumber numberWithInt:[[dictEvent valueForKey:@"user_id"] intValue]],[NSNumber numberWithInt:[[dictEvent valueForKey:@"id"] intValue]]]];

    NSLog(@"Predicate = %@",predicate);

    NSArray *arrSortDescriptors = [NSArray arrayWithObject:sortDescObj];
    [fetchRequest setSortDescriptors:arrSortDescriptors];

    [fetchRequest setEntity:entity];
    [fetchRequest setReturnsDistinctResults:YES];

    [fetchRequest setPredicate:predicate];

    NSArray *arrResult = [context executeFetchRequest:fetchRequest error:&error];

    if ([arrResult count]>0) 
    {                
            NSArray *arrKey = [dictEvent allKeys];
            NSArray *arrValue = [dictEvent allValues];

           NSLog(@"ArrKey : %@\nArrValue : %@",arrKey,arrValue);

           selectedManagedObject = [arrResult objectAtIndex:0];


           for(int i = 0; i < [arrKey count] ; i++) 
           {
               NSLog(@"selectedMng :- %@",selectedManagedObject);
               NSLog(@"KEY: %@\t: %@",[arrKey objectAtIndex:i],[arrValue objectAtIndex:i]);
               if ([[arrKey objectAtIndex:i]isEqualToString:@"id"]) 
               {
                  [selectedManagedObject setValue:[arrValue objectAtIndex:i] forKey:@"event_id"]; 
               }
               else if([[arrKey objectAtIndex:i]isEqualToString:@"invited_status"])
               {
                   [selectedManagedObject setValue:[arrValue objectAtIndex:i] forKey:@"invite_status"];
               }
               else
               {
                   [selectedManagedObject setValue:[arrValue objectAtIndex:i] forKey:[arrKey objectAtIndex:i]];
               }

           }
           if (! [selectedManagedObject.managedObjectContext save:&error])  
           {
               NSLog(@"updateEntityIntoDataBaseNamed - Error :: %@", [error localizedDescription]);
           }
      // }

    }
}

Answer 1

您无法在stringWithFormat中使用predicateWithFormat。你的谓词应该是这样的：

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"user_id=%@ and event_id=%@",
    [NSNumber numberWithInt:[[dictEvent valueForKey:@"user_id"] intValue]],
    [NSNumber numberWithInt:[[dictEvent valueForKey:@"id"] intValue]]
];

Answer 2

除了修改@Martin

建议的谓词外

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"user_id=%@ && event_id=%@",
    [NSNumber numberWithInt:[[dictEvent valueForKey:@"user_id"] intValue]],
    [NSNumber numberWithInt:[[dictEvent valueForKey:@"id"] intValue]]
];

请注意，在两种情况下，您使用非匹配键更新对象：这适用于id和event_id，以及invite_status和invite_status。

使用Core Data更新数据库

2 个答案: