确定核心数据模型中何时有新版本

问题描述

简短问题:

仅当我的核心数据模型已更改(新实体，新属性等)时，我才想在我的应用中运行特定代码.如何确定模型是否已更改?

I want to run a certain code in my app only if my Core Data model has changed (new entities, new properties, etc). How can I determine if the model has changed or not?

只需一些伪代码:

    if (current_model_version != previous_model_version) {
    //do some code
    } else {
    // do some other code
    }

我猜我可能会使用versionHashes或isConfiguration:compatibleWithStoreMetadata:来做到这一点，但我不确定如何做到.

I'm guessing I might use versionHashes to do this, or isConfiguration:compatibleWithStoreMetadata:, but I'm not certain how.

为清晰起见，需要进行一些现在"为当前"，而上次应用程序启动"为上一个".

Some editing for clarity: 'current' as in 'now' and 'previous' as in 'last time app was launched.'

推荐答案

答案似乎是 isConfiguration:compatibleWithStoreMedia:.

我在这里找到了一些有用的信息:

I found some useful information here:

http://mipostel. com/index.php/home/70-core-data-migration-standard-migration-part-2

我是这样设置的:

- (BOOL)modelChanged
{
    NSError *error;
    NSURL * sourceURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"db.sqlite"];
    NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:sourceURL error:&error];
    BOOL isCompatible = [[self managedObjectModel] isConfiguration:nil compatibleWithStoreMetadata:sourceMetadata];

    return isCompatible;

}

'self'是我的共享数据存储，而不必一定要去那里.

'self' is my shared data store, not that it necessarily has to go there.

deanWombourne指出，这实际上是确定是否可以自动迁移数据，因此这并不是我提出的问题的解决方案.在这种情况下，它确实满足了我的需求.

deanWombourne points out that what this really does is determine whether or not the data can be automatically migrated, so it's not exactly the solution to the problem I posed. It does serve my needs in this case.

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