我继续得到“保存操作失败”在我的XCode数据模型的任何更改后

问题描述

我开始使用Core Data进行iPhone开发。我开始创建一个非常简单的实体（称为评估）只有一个字符串属性（称为evaluationTopic）。我有以下代码插入一个新的字符串：

I started using Core Data for iPhone development. I started out by creating a very simple entity (called Evaluation) with just one string property (called evaluationTopic). I had following code for inserting a fresh string:

- (void)insertNewObject {

    // Create a new instance of the entity managed by the fetched results controller.
    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity];
    NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

    // If appropriate, configure the new managed object.
    [newManagedObject setValue:@"My Repeating String" forKey:@"evaluationTopic"];

    // Save the context.
    NSError *error;
    if (![context save:&error]) {
        // Handle the error...
    }

    [self.tableView reloadData];

}

我的重复字符串将被添加到表视图，并在持久存储。

This worked perfectly fine and by pushing the +button a new "My Repeating String" would be added to the table view and be in persistent store.

然后我按设计 - >添加模型版本在XCode。我向现有实体添加了三个实体，并向现有的评估实体添加了新属性。然后，我通过按下文件 - >新建文件 - >管理对象类创建了一个新的文件，并为我的四个实体创建了一个新的.h和.m文件，包括Evaluation实体与Evaluation.h和评估m。现在我通过设置设计 - >数据模型 - >设置当前版本更改了模型版本。完成所有这一切后，我改变了我的insertMethod：

I then pressed "Design -> Add Model Version" in XCode. I added three entities to the existing entity and also added new properties to the existing "Evaluation" entity. Then, I created new files off the entities by pressing "File -> New File -> Managed Object Classes" and created a new .h and .m file for my four entities, including the "Evaluation" entity with Evaluation.h and Evaluation.m. Now I changed the model version by setting "Design -> Data Model -> Set Current Version". After having done all this, I changed my insertMethod:

- (void)insertNewObject {

    // Create a new instance of the entity managed by the fetched results controller.
    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity];
    Evaluation *evaluation = (Evaluation *) [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

    // If appropriate, configure the new managed object.
    [evaluation setValue:@"My even new string" forKey:@"evaluationSpeechTopic"];

    // Save the context.
    NSError *error;
    if (![context save:&error]) {
        // Handle the error...
    }

    [self.tableView reloadData];

}

每次我想添加一行模拟器崩溃，我得到以下：

This does not work though! Every time I want to add a row the simulator crashes and I get the following:

"NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores.  It cannot perform a save operation.'"

关于在更改数据模型上的任何内容后创建新版本，但为什么这仍然出现？我需要做任何映射（即使我只是添加了以前不存在的实体和属性）。在苹果开发教程中，这听起来很容易，但我一直在努力这个很长一段时间，从来没有改变模型版本后工作。

I had this error before I knew about creating new version after changing anything on the datamodel, but why is this still coming up? Do I need to do any mapping (even though I just added entities and properties that did not exist before?). In the Apple Dev tutorial it sounds very easy but I have been struggling with this for long time, never worked after changing model version.

推荐答案

p>您在应用程序代理中创建persistentStoreCoordinator时是否设置了NSMigratePersistentStoresAutomaticallyOption和NSInferMappingModelAutomaticallyOption选项？

Do you have NSMigratePersistentStoresAutomaticallyOption and NSInferMappingModelAutomaticallyOption options set when you create your persistentStoreCoordinator in the App Delegate?

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }

    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"database.sqlite"]];

    NSError *error = nil;
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) {
        // Handle error
    }    

    return persistentStoreCoordinator;
}

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