使用循環來填充coredata的sqlite數據庫

Question

我第一次使用coredata關係。我有兩個實體School和Book，這些屬性具有以下屬性。 學校：id，userid，權限 書名：id，名稱，描述，持續時間，小時。 School和Book之間有一對多的關係。我的目標是從Book based School.userid獲取數據使用關係，我可以實現它。以下是我用於保存和讀取的代碼。

- (IBAction)save:(id)sender { 
    NSManagedObjectContext *context = [self managedObjectContext]; 

    NSManagedObject *School = [NSEntityDescription insertNewObjectForEntityForName:@"School" inManagedObjectContext:context]; 
    [School setValue:self.idTextField.text forKey:@"id"]; 
    [School setValue:self.userIdTextField.text forKey:@"userid"]; 
    [School setValue:self.permissionTextField.text forKey:@"permission"]; 

    NSManagedObject *Book = [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:context]; 
    [Book setValue:self.Id.text forKey:@"id"]; 
    [Book setValue:self.nameTextField.text forKey:@"name"]; 
    [Book setValue:self.descriptionTextField.text forKey:@"discription"]; 
    [Book setValue:self.hoursTextField.text forKey:@"hours"]; 
    [Book setValue:self.durationTextField.text forKey:@"duration"]; 
    [Book setValue:School forKey:@"School"]; 



    [School mutableSetValueForKey:@"Book"]; 

    NSError *error = nil; 
    // Save the object to persistent store 
    if (![context save:&error]) { 
     NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); 
    } 

    [self dismissViewControllerAnimated:YES completion:nil]; 
} 

現在，我想自動填充coredata，而不需要通過接口來保存使用loops.I能夠循環工作，直到填充學校。但是，我無法使用循環對特定用戶ID填充Book表。請指導如何實現此目的。任何幫助和建議將不勝感激。提前感謝。

Answer 1

請在每個if語句添加for循環，並設置您選擇的值

if(i>0 &&i<=100) 
      { 
       [School setValue:@"Apple" forKey:@"userid"]; 

       for(int j = 0; j < 10; j++) { 
        NSManagedObject *Book= [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:context]; 
        [Book setValue:[NSString stringWithFormat:@"%i", j + 10] forKey:@"id"]; 
        [Book setValue:[NSString stringWithFormat:@"Name: %i", j] forKey:@"name"]; 
        [Book setValue:[NSString stringWithFormat:@"%i", j] forKey:@"hours"]; 

        [Book setValue:School forKey:@"School"]; 

       } 



      } 
else if(i>100 && i<=200){ 
      [School setValue:@"iPhone" forKey:@"userid"]; 
      for(int j = 10; j < 20; j++) { 
        NSManagedObject *wouni = [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:context]; 
        [Book setValue:[NSString stringWithFormat:@"%i", j + 10] forKey:@"id"]; 
        [Book setValue:[NSString stringWithFormat:@"Name: %i", j] forKey:@"name"]; 
        [Book setValue:[NSString stringWithFormat:@"%i", j] forKey:@"hours"]; 


        [Book setValue:School forKey:@"School"]; 

       } 




     } 

注：如果這是逆一個從學校許多關係到wouni（學校的目的之一是與wounis的許多對象）相關 那麼你不需要重新添加wounis學校，因爲CoreData將採取逆關係

最後的照顧，我覺得你不需要下面的語句在每個if條件，

if (![context save:&error]) { 
      NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); 

    } 

只是在功能

對於謂語部分的結尾寫一次，我想你應該添加謂詞是這樣的：

[r setPredicate:[NSPredicate predicateWithFormat:@"SELF.userid = %@",userid]];