核心數據與多對多關係

您好，我爲歌曲實體保存歌詞段數。現在我想更新歌詞核心數據與多對多關係

我用下面的代碼來更新值。但它正在創造新的紀錄..還告訴刪除

- (void)editLyrics { 

    [editBarbutton setTitle:@"Save"]; 



    lyrics = [NSEntityDescription insertNewObjectForEntityForName:@"Lyrics" inManagedObjectContext:managedObjectContext]; 
    lyrics.songLyrics = lyricsTextview.text; 





    lyrics.startTime = startTimeText.text; 






    lyrics.endTime = endTimeText.text; 

    lyrics.lyricsSong = song;  
    NSError *error; 
    // here's where the actual save happens, and if it doesn't we print something out to the onsole 
    if (![managedObjectContext save:&error]) 
    { 
     NSLog(@"Problem saving: %@", [error localizedDescription]); 
    } 
    }

來源

2011-10-17 iProgrammer

你必須讓本發明的目的之前：

NSError *error = nil; 
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; 
[request setEntity:[NSEntityDescription entityForName:@"Lyrics" 
           inManagedObjectContext:self.moc]]; 
[request setPredicate:[NSPredicate predicateWithFormat:@"something what u like to filter"]]; 
NSArray *lyrics = [self.moc executeFetchRequest:request error:&error]; 
if (error) NSLog(@"Failed to executeFetchRequest to data store: %@ in function:%@", [error localizedDescription],NSStringFromSelector(_cmd)); 
lyrics = [lyrics lastObject]

來源

2011-10-17 12:27:03 user170317

我m到處歌詞對象和managedobjectcontext從以前的觀點..你的代碼是不是仍然創造新的記錄 – iProgrammer 2011-10-17 12:37:00

核心數據與多對多關係

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