[問題] Core Data relation沒有作用

看板MacDev作者wrt (一片小蛋糕)時間8年前 (2016/10/04 03:52)推噓2(2推 0噓 5→)

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如題我已經設定好relation 算是蠻簡單的練習而已不過不知道為何我用sql看coredata的資料庫時,發現並沒有正確的幫我建立對應關係例如一個Album只能有一個singer 一個singer可以有很多個Album 然後我去建立資料 singer:A Album:01 singer:A Album:02 singer:A Album:03 這時去看sql資料應該要是 pk singer 1 A 2 A 3 A pk Album singer 1 01 1 2 02 1 3 03 1 但是我跑出來的都是 pk singer 1 A 2 A 3 A pk Album singer 1 01 1 2 02 2 3 03 3 雖然Album有建立與singer的relation,而且最後出來的singer都是Ａ但是總覺得哪裡怪怪的,跟期待的不一樣,原本期待singer(key)都只會是1而已好像coredata並沒有幫我搜尋我建立的singer是不是重複的沒有在建立關係時幫我統一對應到一個這是本來受這樣嗎？還是我哪邊可能有出錯呢？ coredata是用xcdatamodel建立的我檢查singer跟album的relation有箭頭互相指 ---------------------- @interface Album (CoreDataProperties) @property (nullable, nonatomic, retain) NSString *album_name; @property (nullable, nonatomic, retain) Singer *singer; @end ----------------------- @interface Singer (CoreDataProperties) @property (nullable, nonatomic, retain) NSString *name; @property (nullable, nonatomic, retain) NSSet<Album *> *album; @end ----------------------- Singer *singer = [self.appDelegate creatSinger]; singer.name = self.singerField.text; Album *album = [self.appDelegate creatAlbum]; album.album_name = self.albumField.text; album.singer = singer; //建立album與singer關係 ----------------------- - (Singer *) creatSinger { NSManagedObjectContext *moc = [self managedObjectContext]; Singer *singer = [NSEntityDescription insertNewObjectForEntityForName:@"Singer" inManagedObjectContext:moc]; return singer; } - (Album *) creatAlbum { NSManagedObjectContext *moc = [self managedObjectContext]; Album *album = [NSEntityDescription insertNewObjectForEntityForName:@"Album" inManagedObjectContext:moc]; return album; } -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 123.241.102.252 ※ 文章網址: https://www.ptt.cc/bbs/MacDev/M.1475524374.A.46E.html ※ 編輯: wrt (123.241.102.252), 10/04/2016 04:08:32