應用程序崩潰在coredata中的對象ID爲它的主鍵字段

Question

我第一次使用Coredata，我將一些值設置爲userinfo實體，從usergroups實體中提取一些值。

，而這樣做的過程我的申請得到墜毀說：

「以前未分配的對象ID爲它的主鍵 場，這是用於獲得核心數據 對象的永久ID項目。在調用保存managedObjectContext之前，請確保 指定了一個對象ID。

這看起來有點像

[newManagedObject setValue:[newManagedObject assignObjectId] forKey:[newManagedObject 
primaryKeyField]] 

。有問題的產品：

<Userinfo: 0x10695b30> (entity: Userinfo; id: 0x10695b70 <x-coredata://18875EDC-D300-4D63-90FC-181B2487599D-3229-000024DF842CC304/Userinfo/tA6216695-816F-4379-B24C-984AAFD1A8342>; data: 

//讀取值的&修改

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Userinfo" inManagedObjectContext:context]; 
    [fetchRequest setEntity:entity]; 
    NSPredicate *datapredicate = [NSPredicate predicateWithFormat:@"username == %@",usermobileNumber]; 
    [fetchRequest setPredicate:datapredicate]; 

    [context executeFetchRequest:fetchRequest onSuccess:^(NSArray *results){ 
     NSLog(@"results %@",[results valueForKey:@"firstname"]); 
     userinfoObject = [results objectAtIndex:0]; 
     NSLog(@"userinfo %@",userinfoObject); 
//  userinfoObject = [[Userinfo alloc]initWithEntity:[NSEntityDescription entityForName:@"Userinfo" inManagedObjectContext:context] insertIntoManagedObjectContext:context]; 

     [userinfoObject setValue:[userinfoObject valueForKey:@"firstname"] forKey:@"firstname"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"lastname"] forKey:@"lastname"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"email"] forKey:@"email"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"zipcode"] forKey:@"zipcode"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"password"] forKey:@"password"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"dateofbirth"] forKey:@"dateofbirth"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"username"] forKey:@"username"]; 
     [userinfoObject setValue:[userinfoObject valueForKey:@"salutation"] forKey:@"salutation"]; 
//  [userinfoObject setValue:[userinfoObject assignObjectId] forKey:[userinfoObject primaryKeyField]]; 

//添加值

Usergroups *userGroupsObject = [NSEntityDescription insertNewObjectForEntityForName:@"Usergroups" inManagedObjectContext:context]; 
      [userGroupsObject setValue:contactObject.strGroupName forKey:@"groupname"]; 
      [userGroupsObject setValue:[contactsStack objectAtIndex:i] forKey:@"mobile_contacts"]; 
      [userGroupsObject setValue:usermobileNumber forKey:@"mobile_number"]; 
      [userGroupsObject setValue:[userGroupsObject assignObjectId] forKey:[userGroupsObject primaryKeyField]]; 
      NSError *error = nil; 
      if (![context saveAndWait:&error]) { 
       NSLog(@"There was an error! %@", error); 
      } 
      else { 
       NSLog(@"You created Usergroup object!"); 
      } 
      [userinfoObject addUsergroupsObject:userGroupsObject]; 

Answer 1

你應該提供更多的代碼....... ...

一般添加新條目將如下所示

FormField *info = [NSEntityDescription 
        insertNewObjectForEntityForName:@"FormField" 
        inManagedObjectContext:managedObjectContext]; 


[info setValue: @"string data to insert" forKey:@"fieldValue"]; 
NSError *error; 
[managedObjectContext save:&error] 

和檢索的入口看起來像這樣

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
[fetchRequest setEntity:[NSEntityDescription entityForName:@"entityName" 
            inManagedObjectContext:managedObjectContext]]; 

NSError *error; 
NSArray* data_ = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; 

Answer 2

的assignObjectID和primaryKeyField方法擺脫那些誰正在努力，因爲他們是StackMob具體的方法來回答這個問題。它們不直接與核心數據ID進行交互，只是將一個隨機生成的UUID分配給映射到數據庫主鍵字段（StackMob服務器）的屬性。事實上，在調用save之前必須執行此操作，因爲增量存儲實現會使用該字符串ID在重寫的obtainPermanentIDsForObjects：方法中創建永久的Core Data ID。

我的猜測是你有一個託管對象，在它被保存之前，永遠不會爲映射到數據庫主鍵字段的屬性分配一個值。在導致崩潰的保存之前，設置斷點並打印出託管對象上下文的插入對象（即[self.managedObjectContext insertedObjects]）。這應該讓你知道什麼對象導致崩潰，並且你可以相應地調整你的代碼。