iPhone Core Data 轻量级迁移:无法合并模型 [英] iPhone Core Data Lightweight Migration: Can't merge models

问题描述

我刚开始使用 iPhone 核心数据，但在轻量级迁移中遇到了问题.

I just started with iPhone core data and I ran into a problem in lightweight migration.

• 我在旧模型中添加了两个新字段
• 重新生成模型类文件
• 将新模型版本设为当前版本

• 在生成的模板中的AppDelegate中添加如下代码

• I added two new fields to my old model
• Regenerated the model class files
• Made the new model version as current version

• Added the following code in AppDelegate in the template generated

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {

if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {

最后，我在运行应用程序之前做了一个干净的构建.

Then at last, I did a clean build before running the app.

当应用程序崩溃时，我收到以下错误...

I get the following error when the app crashes...

The operation couldn’t be completed. (Cocoa error 134140.)" UserInfo=0x622b350 {reason=Can't find or automatically infer mapping model for migration

现在调试我添加了以下代码...

Now to debug I added the following code...

    NSError *error = nil;
    NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:storeURL error:&error];

    if (!sourceMetadata) {
        NSLog(@"sourceMetadata is nil");
    } else {
        NSLog(@"sourceMetadata is %@", sourceMetadata);
    }

这将显示以下结果...

This displays the following result...

2011-01-20 18:18:41.018 MyApp[4438:207] sourceMetadata is {
    NSPersistenceFrameworkVersion = 248;
    NSStoreModelVersionHashes =     {
        Fugitive = <e33370b6 e7ca3101 f91d2595 1e8bfe01 3e7fb4de 6ef2a31d 9e50237b b313d390>;
    };
    NSStoreModelVersionHashesVersion = 3;
    NSStoreModelVersionIdentifiers =     (
    );
    NSStoreType = SQLite;
    NSStoreUUID = "E711F65F-3C5A-4889-872B-6541E4B2863A";
    "_NSAutoVacuumLevel" = 2;
}

我检查了应用程序包 > MyApp.momd > VersionInfo.plist 文件

I checked the app bundle > MyApp.momd > VersionInfo.plist file

它有以下内容...

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>NSManagedObjectModel_CurrentVersionName</key>
    <string>MyApp 2</string>
    <key>NSManagedObjectModel_VersionHashes</key>
    <dict>
        <key>MyApp</key>
        <dict>
            <key>Fugitive</key>
            <data>
            4zNwtufKMQH5HSWVHov+AT5/tN5u8qMdnlAje7MT05A=
            </data>
        </dict>
        <key>MyApp 2</key>
        <dict>
            <key>Fugitive</key>
            <data>
            N58Lf4BNpACzrsHAb1+BQImgjsBZ+u5G0wGUyt84+Ec=
            </data>
        </dict>
    </dict>
</dict>
</plist>

我在这里遗漏了什么?

更新:问题是我在模型中遗漏了一个默认值属性.

UPDATE: The problem turned out to be a default value attribute that I had missed in the model.

推荐答案

您可以尝试强制 Core Data 推断映射模型:

You might try forcing Core Data to infer a mapping model:

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

如果对模型的更改微不足道，那么 Core Data 可能能够推断出映射模型.如果失败，那么您可能需要创建一个映射模型(并恢复到您当前使用的选项).

If the changes to your model were trivial, then Core Data may be able to infer a mapping model. If that fails, then you will probably need to create a mapping model (and revert to the options that you are currently using).

映射模型很容易创建.但是请注意，如果您更改数据模型，那么您也需要更新映射.

Mapping models are easy to create. Be mindful, though, if you change a data model then you will need to update the mapping, too.

您可能想查看 这篇 SO 帖子.

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