Question

我想查看NSManagedObjectModel的版本，因此在更新时，我想删除所有托管对象，并从服务器下载所有记录并重新填充本地持久性存储。

知道如何查看最新版本的模型吗？

NSManagedObjectModel班级参考

entityVersionHashesByName
versionIdentifiers

但我不认为这些是我需要的。

Answer 1

您可以通过以下方式获取该版本：

NSSet *versionIdentifiers = [[self managedObjectModel] versionIdentifiers];
NSLog(@"Which Current Version is our .xcdatamodeld file set to? %@", versionIdentifiers);

- (BOOL)checkForMigration

            NSManagedObjectModel *destinationModel = [self.persistentStoreCoordinator managedObjectModel];
            //Our Source 1 is going to be incompatible with the Version 2 Model, our Source 2 won't be...
            BOOL pscCompatible = [destinationModel isConfiguration:configuration compatibleWithStoreMetadata:sourceMetadata];
            NSLog(@"Is the STORE data COMPATIBLE? %@", (pscCompatible==YES) ?@"YES" :@"NO");

            if (pscCompatible == NO)
            {
                migrationSuccess = [self performMigrationWithSourceMetadata:sourceMetadata toDestinationModel:destinationModel];
            }
    }


- (BOOL)performMigrationWithSourceMetadata: (NSDictionary *) sourceMetadata toDestinationModel: (NSManagedObjectModel *) destinationModel
{
    BOOL migrationSuccess = NO;

    //Initialise a Migration Manager...
    NSManagedObjectModel *sourceModel = [NSManagedObjectModel mergedModelFromBundles: nil
                                                                    forStoreMetadata: sourceMetadata];

    //Perform the migration...

    if (sourceModel)
    {
        NSMigrationManager *standardMigrationManager = [[NSMigrationManager alloc]
                                                        initWithSourceModel: sourceModel
                                                        destinationModel: destinationModel];

        //Retrieve the appropriate mapping model...
        NSMappingModel *mappingModel = [NSMappingModel mappingModelFromBundles: nil
                                                                forSourceModel: sourceModel
                                                              destinationModel: destinationModel];

        if (mappingModel)
        {
            NSError *error = nil;
            NSString *storeSourcePath = [[self applicationDocumentsDirectoryString] stringByAppendingPathComponent: @"SQL-FILE-V1"];
            NSURL *storeSourceUrl = [NSURL fileURLWithPath: storeSourcePath];
            NSString *storeDestPath = [[self applicationDocumentsDirectoryString] stringByAppendingPathComponent: @"SQL-File-V2.sqlite"];
            NSURL *storeDestUrl = [NSURL fileURLWithPath: storeDestPath];


            //Pass nil here because we don't want to use any of these options:
            //NSIgnorePersistentStoreVersioningOption, NSMigratePersistentStoresAutomaticallyOption, or NSInferMappingModelAutomaticallyOption
            NSDictionary *sourceStoreOptions = nil;
            NSDictionary *destinationStoreOptions = nil;
            migrationSuccess = [standardMigrationManager migrateStoreFromURL: storeSourceUrl
                                                                        type: NSSQLiteStoreType
                                                                     options: sourceStoreOptions
                                                            withMappingModel: mappingModel
                                                            toDestinationURL: storeDestUrl
                                                             destinationType: NSSQLiteStoreType
                                                          destinationOptions: destinationStoreOptions
                                                                       error: &error];
            NSLog(@"MIGRATION SUCCESSFUL? %@", (migrationSuccess == YES) ? @"YES" : @"NO");
        }
    }
    else
    {
        //TODO: Error to user...
        NSLog(@"checkForMigration FAIL - No Mapping Model found!");
        abort();
    }
    return migrationSuccess;
} //END

获取NSManagedObjectModel的版本

1 个答案: