迁移Core Data存储时出现错误消息 [英] Error message when migrating Core Data store

问题描述

问题：

我有一些很简单的代码> __ NSArrayM replaceObjectAtIndex：withObject：

]：object不能为nil

代码：

  NSPersistentStore * oldStore = [_persistentStoreCoordinator persistentStores] [0] 
 
 if（oldStore）{
 
 @try {
 
 [_persistentStoreCoordinator migratePersistentStore：oldStore 
 toURL：[self storeURL] 
 options：@ {NSPersistentStoreRemoveUbiquitousMetadataOption：@YES} 
 withType：NSSQLiteStoreType error：& error]; 
 
} 
 @catch（NSException * ex）{
 
 NSLog（@Exception：％@，ex.description）; 
 
} 
 
} 
  

更多信息：

• 如果没有数据，则不会发生异常。而是相同的函数设置一个错误，用userInfo无法添加相同的存储两次。


• 我目前正在做一个小的简单项目

解决方案

找到了it！

显然，当您的iCloud网址和本地网址相同时，Core Data不喜欢迁移。我认为这不应该重要，因为真的，iCloud数据存储在自己的目录。但是，似乎在迁移期间，使用相同的名称会导致问题。 BAZINGA！

轻松修复 - 只需这样做：

  - （NSURL *）storeURL {
 
 NSURL * documentsDirectory = [[NSFileManager defaultManager] URLForDirectory：NSDocumentDirectory inDomain：NSUserDomainMask appropriateForURL：nil create：YES error：NULL]; 
 
 if（iCloudEnabled]）{
 return [documentsDirectory URLByAppendingPathComponent：@iCloudEventData.sqlite]; 
} else {
 return [documentsDirectory URLByAppendingPathComponent：@EventData.sqlite]; 
} 
 
} 
  

The Problem:

I've got some pretty simple code (below) that causes an exception during 'migratePersistentStore' with the error message

Exception:*** -[__NSArrayM replaceObjectAtIndex:withObject:]: object cannot be nil

The Code:

NSPersistentStore * oldStore = [_persistentStoreCoordinator persistentStores][0];

if (oldStore) {

    @try {

        [_persistentStoreCoordinator migratePersistentStore:oldStore 
              toURL:[self storeURL] 
              options: @{ NSPersistentStoreRemoveUbiquitousMetadataOption : @YES } 
              withType:NSSQLiteStoreType error:&error];

    }
    @catch(NSException* ex) {

        NSLog(@"Exception:%@", ex.description);

    }

}

Further Info:

• It appears that if no data is present, the exception does not occur. Instead the same function sets an error, with userInfo "Can't add the same store twice".
• I'm currently making a small simple project to try and replicate the problem, I'll post a link here once it's done.

解决方案

Found it!

Apparently, Core Data doesn't like migration when your iCloud URL and local URL are the same. I thought this shouldn't matter because really, iCloud data is stored in its own directory. BUT, it seems during migration, using the same name causes problems. BAZINGA!

Easy fix - just do something like this:

- (NSURL *)storeURL {

    NSURL * documentsDirectory = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:NULL];

    if (iCloudEnabled]) {
        return [documentsDirectory URLByAppendingPathComponent:@"iCloudEventData.sqlite"];
    } else {
        return [documentsDirectory URLByAppendingPathComponent:@"EventData.sqlite"];
    }

}

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