iPhone - 添加核心數據問題

Question

這是簡單的，但我似乎無法找到問題。新元素沒有被添加到數據庫中，我在代碼中沒有收到任何錯誤。

這裏是add方法

- (void) addPressed:(NSNotification *) message 
{ 
// Insert a new record in the database 
Track *track2 = [NSEntityDescription insertNewObjectForEntityForName: @"Track" inManagedObjectContext: managedObjectContext]; 

[managedObjectContext save: &error]; 

tracks = [self fetchTracks]; 


// Insert a new item in the table's data source 
[tracks insertObject: track2 atIndex: 0]; 

// Insert a new row in the table 
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection: 0]; 

addTrack.track = [tracks objectAtIndex: indexPath.row]; 

NSLog(@"here"); 

[[NSNotificationCenter defaultCenter] postNotificationName:@"choosePressed" object:self]; 


} 

附加被稱爲它發送一個消息到用戶拿起從mpmediapicker歌曲另一個視圖控制器之後，然後點擊保存按鈕，其選擇該方法

- (void) finishedEditing 
{ 


if(start.text.length == 0) 
{ 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Warning" message: @"You must fill out all fields" delegate: self cancelButtonTitle: @"OK" otherButtonTitles: nil]; 
    alert.tag = 1; 
    [alert show]; 
    [alert release]; 
} 
else if(duration.text.length == 0) 
{ 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Warning" message: @"You must fill out all fields" delegate: self cancelButtonTitle: @"OK" otherButtonTitles: nil]; 
    alert.tag = 1; 
    [alert show]; 
    [alert release]; 
} 
else if(name.text.length == 0) 
{ 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Warning" message: @"You must fill out all fields" delegate: self cancelButtonTitle: @"OK" otherButtonTitles: nil]; 
    alert.tag = 1; 
    [alert show]; 
    [alert release]; 
} 
else if(songLabel.text.length == 0) 
{ 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Warning" message: @"You must select a song" delegate: self cancelButtonTitle: @"OK" otherButtonTitles: nil]; 
    alert.tag = 1; 
    [alert show]; 
    [alert release]; 
}  
else 
{ 
    if (repeat) 
    { 
     track.title = NULL; 
     track.name = NULL; 
     repeat = NO; 

    } 
    else 
    { 
     songLabel.text = @""; 
     artistLabel.text = @""; 
     [self viewWillDisappear: YES]; 
     [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil]; 
     track.name = name.text; 
     track.duration = duration.text; 
     track.startloc = start.text; 
     track.title = [song valueForProperty:MPMediaItemPropertyTitle]; 
     NSManagedObjectContext *context = track.managedObjectContext; 
     NSError *error = nil; 
     [context save: &error]; 

     [[NSNotificationCenter defaultCenter] postNotificationName:@"myTraxsTab" object:self]; 

    } 


} 

} 

我使用NSFetchRequest而不是fetchedResults控制器。繼承人的代碼。

request = [[NSFetchRequest alloc] init]; 
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey: @"name" ascending: YES]; 
sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; 
request.sortDescriptors = sortDescriptors; 
[sortDescriptor release]; 
error = nil; 
entity = [NSEntityDescription entityForName: @"Track" inManagedObjectContext: managedObjectContext]; 
request.entity = entity; 

UPDATE

好了，所以我添加了一行打印陣列else語句這裏

else 
    { 
     songLabel.text = @""; 
     artistLabel.text = @""; 
     [self viewWillDisappear: YES]; 
     [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil]; 
     track.name = name.text; 
     track.duration = duration.text; 
     track.startloc = start.text; 
     track.title = [song valueForProperty:MPMediaItemPropertyTitle]; 
     NSManagedObjectContext *context = track.managedObjectContext; 
     NSError *error = nil; 
     [context save: &error]; 

     NSLog(@"array: %@", tracks); 

     [[NSNotificationCenter defaultCenter] postNotificationName:@"myTraxsTab" object:self]; 

    } 

而這正是它的打印。我不知道我缺少什麼。它讓我發瘋。我明顯增加了名稱，持續時間和開始標籤的值。

array: (
"<Track: 0x136d80> (entity: Track; id: 0x13a120 <x-coredata://9D789618-64C1-40BF-9F15-BA6A3EA715D3/Track/p7> ; data: {\n duration = nil;\n name = nil;\n startloc = nil;\n title = nil;\n})" 
) 

Answer 1

如果你沒有任何 美眉 崩潰（而不是隻在這種情況下），首先我要替換的字符串：喜歡的東西

[managedObjectContext save: &error]; 

：

// Save the managed object context. 
NSError *error = nil; 
if (![self.managedObjectContext save:&error]) { 
    NSLog(@"Failed to save object to managed object context: %@, %@", error, [error userInfo]); 
} 

也許（我認爲最有可能的），NSlog在這種情況下會給你一些信息。 在任何情況下，男人，儲蓄是一個相當危險的操作，你不應該離開它，沒有額外的，至少很小，檢查。

祝你好運！

編輯：
你能張貼如何實際上您從數據庫中的對象的抓取。據我瞭解，你在這裏執行它：

tracks = [self fetchTracks]; 

但那裏有什麼？
另外，我覺得有點迷惑frase：

Im using a NSFetchRequest not a fetchedResults controller.

創建NSFetchRequest，以對象描述，你想從數據庫中檢索（提取）的東西。你做正確的，但我並不在你實際上使用這個請求，那麼...
對於檢索NSFetchedResultsController的目的正在使用的代碼中看到。 你把它設置爲smth。像：

NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] 
                 initWithFetchRequest:request 
                 managedObjectContext:self.managedObjectContext 
                 sectionNameKeyPath:nil cacheName:nil]; 
aFetchedResultsController.delegate = self; 
self.fetchedResultsController = aFetchedResultsController; 

，然後進行實際的獲取，你做的不便。像：

if (![self.fetchedResultsController performFetch:&error]) { 
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
} 

（在此之後，你可以從fetchedResultsController所有對象）

OR，如果你不希望使用控制器，直接取到數組：

NSError *error = nil; 
NSArray *array = [managedObjectContext executeFetchRequest:request error:&error]; 
if (array == nil) 
{ 
    // Deal with error... 
}