我已啓用Core Data模型的版本控制，並且使用輕量級遷移。我的代碼總是試圖執行輕量級遷移，然後如果因爲模型不兼容而失敗，它將回退到刪除所有現有數據並從服務器重新獲取。 所以輕量級遷移僅用於提高效率，而不是正確性所必需的。CoreData版本控制和阻止輕量級遷移
我現在想要做的是對我的模型進行更改，理論上輕量級遷移可以處理，但實際上我需要來自服務器的新數據。我想以某種方式標記模型並且不能通過輕量級遷移進行升級。例如，如果字段名稱未更改，但該字段的含義已更改，舊代碼與新代碼庫不兼容。 （這只是一個例子。）
有沒有人找到一種方法來標記兩個模型不兼容，所以輕量級的遷移不會升級它們？
我以前一直在努力解決同樣的問題。
我有一個方法，將試圖使用映射模型遷移數據，這是你應該使用，如果你要關閉輕量級遷移。
如果你不打算做很多花哨的數據映射，xcode會自動創建一個映射模型，它可以像輕量級遷移一樣工作。您只需在每次向Core Data添加新版本時創建一個新的「Mapping Model」文件。只需進入「文件 - >新建 - >新建文件」，在覈心數據下，應該有一個映射模型模板。選擇它並選擇源和目標版本。
我沒有我的代碼公開可用在github上，所以我只是在這裏發佈遷移方法。
- (BOOL)progressivelyMigrateURL:(NSURL*)sourceStoreURL ofType:(NSString*)type toModel:(NSManagedObjectModel*)finalModel
{
NSError *error = nil;
// if store dosen't exist skip migration
NSString *documentDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
if(![NSBundle pathForResource:@"YongoPal" ofType:@"sqlite" inDirectory:documentDir])
{
migrationProgress = 1.0;
[self performSelectorOnMainThread:@selector(updateMigrationProgress) withObject:nil waitUntilDone:YES];
// remove migration view
[self.migrationView performSelectorOnMainThread:@selector(setHidden:) withObject:[NSNumber numberWithBool:YES] waitUntilDone:YES];
[self.migrationView performSelectorOnMainThread:@selector(removeFromSuperview) withObject:nil waitUntilDone:YES];
self.migrationView = nil;
self.migrationProgressLabel = nil;
self.migrationProgressView = nil;
self.migrationSpinner = nil;
return YES;
}
//START:progressivelyMigrateURLHappyCheck
NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:type URL:sourceStoreURL error:&error];
if (!sourceMetadata)
{
return NO;
}
if ([finalModel isConfiguration:nil compatibleWithStoreMetadata:sourceMetadata])
{
migrationProgress = 1.0;
[self performSelectorOnMainThread:@selector(updateMigrationProgress) withObject:nil waitUntilDone:YES];
// remove migration view
[self.migrationView performSelectorOnMainThread:@selector(setHidden:) withObject:[NSNumber numberWithBool:YES] waitUntilDone:YES];
[self.migrationView performSelectorOnMainThread:@selector(removeFromSuperview) withObject:nil waitUntilDone:YES];
self.migrationView = nil;
self.migrationProgressLabel = nil;
self.migrationProgressView = nil;
self.migrationSpinner = nil;
error = nil;
return YES;
}
else
{
migrationProgress = 0.0;
[self.migrationView performSelectorOnMainThread:@selector(setHidden:) withObject:NO waitUntilDone:YES];
[self performSelectorOnMainThread:@selector(updateMigrationProgress) withObject:nil waitUntilDone:YES];
}
//END:progressivelyMigrateURLHappyCheck
//START:progressivelyMigrateURLFindModels
//Find the source model
NSManagedObjectModel *sourceModel = [NSManagedObjectModel mergedModelFromBundles:nil forStoreMetadata:sourceMetadata];
if(sourceModel == nil)
{
NSLog(@"%@", [NSString stringWithFormat:@"Failed to find source model\n%@", [sourceMetadata description]]);
return NO;
}
//Find all of the mom and momd files in the Resources directory
NSMutableArray *modelPaths = [NSMutableArray array];
NSArray *momdArray = [[NSBundle mainBundle] pathsForResourcesOfType:@"momd" inDirectory:nil];
for (NSString *momdPath in momdArray)
{
NSAutoreleasePool *pool = [NSAutoreleasePool new];
NSString *resourceSubpath = [momdPath lastPathComponent];
NSArray *array = [[NSBundle mainBundle] pathsForResourcesOfType:@"mom" inDirectory:resourceSubpath];
[modelPaths addObjectsFromArray:array];
[pool drain];
}
NSArray* otherModels = [[NSBundle mainBundle] pathsForResourcesOfType:@"mom" inDirectory:nil];
[modelPaths addObjectsFromArray:otherModels];
if (!modelPaths || ![modelPaths count])
{
//Throw an error if there are no models
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setValue:@"No models found in bundle" forKey:NSLocalizedDescriptionKey];
//Populate the error
error = [NSError errorWithDomain:@"com.yongopal.coredata" code:500 userInfo:dict];
if([[self.prefs valueForKey:@"debugMode"] isEqualToString:@"Y"])
{
NSLog(@"error: %@", error);
}
return NO;
}
//END:progressivelyMigrateURLFindModels
//See if we can find a matching destination model
//START:progressivelyMigrateURLFindMap
NSMappingModel *mappingModel = nil;
NSManagedObjectModel *targetModel = nil;
NSString *modelPath = nil;
for(modelPath in modelPaths)
{
targetModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:[NSURL fileURLWithPath:modelPath]];
mappingModel = [NSMappingModel mappingModelFromBundles:nil forSourceModel:sourceModel destinationModel:targetModel];
//If we found a mapping model then proceed
if(mappingModel)
{
break;
}
else
{
//Release the target model and keep looking
[targetModel release];
targetModel = nil;
}
}
//We have tested every model, if nil here we failed
if (!mappingModel)
{
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setValue:@"No mapping models found in bundle" forKey:NSLocalizedDescriptionKey];
error = [NSError errorWithDomain:@"com.yongopal.coredata" code:500 userInfo:dict];
if([[self.prefs valueForKey:@"debugMode"] isEqualToString:@"Y"])
{
NSLog(@"error: %@", error);
}
return NO;
}
//END:progressivelyMigrateURLFindMap
//We have a mapping model and a destination model. Time to migrate
//START:progressivelyMigrateURLMigrate
NSMigrationManager *manager = [[NSMigrationManager alloc] initWithSourceModel:sourceModel destinationModel:targetModel];
// reg KVO for migration progress
[manager addObserver:self forKeyPath:@"migrationProgress" options:NSKeyValueObservingOptionNew context:NULL];
NSString *modelName = [[modelPath lastPathComponent] stringByDeletingPathExtension];
NSString *storeExtension = [[sourceStoreURL path] pathExtension];
NSString *storePath = [[sourceStoreURL path] stringByDeletingPathExtension];
//Build a path to write the new store
storePath = [NSString stringWithFormat:@"%@.%@.%@", storePath, modelName, storeExtension];
NSURL *destinationStoreURL = [NSURL fileURLWithPath:storePath];
if (![manager migrateStoreFromURL:sourceStoreURL type:type options:nil withMappingModel:mappingModel toDestinationURL:destinationStoreURL destinationType:type destinationOptions:nil error:&error])
{
if([[self.prefs valueForKey:@"debugMode"] isEqualToString:@"Y"])
{
NSLog(@"error: %@", error);
}
[targetModel release];
[manager removeObserver:self forKeyPath:@"migrationProgress"];
[manager release];
return NO;
}
[targetModel release];
[manager removeObserver:self forKeyPath:@"migrationProgress"];
[manager release];
//END:progressivelyMigrateURLMigrate
//Migration was successful, move the files around to preserve the source
//START:progressivelyMigrateURLMoveAndRecurse
NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString];
guid = [guid stringByAppendingPathExtension:modelName];
guid = [guid stringByAppendingPathExtension:storeExtension];
NSString *appSupportPath = [storePath stringByDeletingLastPathComponent];
NSString *backupPath = [appSupportPath stringByAppendingPathComponent:guid];
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager moveItemAtPath:[sourceStoreURL path] toPath:backupPath error:&error])
{
if([[self.prefs valueForKey:@"debugMode"] isEqualToString:@"Y"])
{
NSLog(@"error: %@", error);
}
//Failed to copy the file
return NO;
}
//Move the destination to the source path
if (![fileManager moveItemAtPath:storePath toPath:[sourceStoreURL path] error:&error])
{
if([[self.prefs valueForKey:@"debugMode"] isEqualToString:@"Y"])
{
NSLog(@"error: %@", error);
}
//Try to back out the source move first, no point in checking it for errors
[fileManager moveItemAtPath:backupPath toPath:[sourceStoreURL path] error:nil];
return NO;
}
//We may not be at the "current" model yet, so recurse
return [self progressivelyMigrateURL:sourceStoreURL ofType:type toModel:finalModel];
//END:progressivelyMigrateURLMoveAndRecurse
}
這是我從某些核心數據手冊中獲得的一種編輯版本，我不記得標題了。我希望我能給作者一點功勞。 ：S
當心，我在這裏的一些代碼，你應該在你執行刪除。這主要是我用來更新遷移進度視圖的東西。
您可以使用此方法，像這樣：
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"YongoPal.sqlite"];
// perform core data migrations if necessary
if(![self progressivelyMigrateURL:storeURL ofType:NSSQLiteStoreType toModel:self.managedObjectModel])
{
// reset the persistent store on fail
NSString *documentDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
NSError *error = nil;
[[NSFileManager defaultManager] removeItemAtPath:[NSBundle pathForResource:@"YongoPal" ofType:@"sqlite" inDirectory:documentDir] error:&error];
}
else
{
NSLog(@"migration succeeded!");
}
記住您使用此之前刪除輕量級遷移選項。
Apple的Core Data Model Versioning and Data Migration Programming Guide解決了如果「你有兩個版本的模型，Core Data通常會認爲你想被識別爲不同的模型」，我認爲這就是你所要求的。
答案是設置versionHashModifier你的實體或屬性的新模式之一。
在你的例子中，你會這樣做的意義已經改變的領域。
我不遵循這段代碼如何解決我的問題。重申一下，我需要一種說法，兩種模式不兼容。我應該在XCode中創建映射模型文件後做些什麼？ – vm2000 2012-03-07 20:40:55
您創建映射模型試圖從內部的Xcode（4.x版）查看它後，它應該拉起實體映射列表和屬性映射。從屬性映射列表中，您應該看到目標和值表達式。只需從遷移中刪除您希望從EXCLUDE中移除的屬性的值表達式（應該看起來像$ source。{attribute_name}），以便它是空的。當你運行漸進式遷移URL：ofType：toModel：方法時，它將遷移除空值表達式的屬性以外的所有內容。 – 2012-03-08 09:42:45
該方法來自Marcus S. Zarra的「核心數據：用於在Mac OSX上保存數據的Apples API」。我認爲它現在被稱爲「核心數據：iOS，OS X和iCloud的數據存儲和管理」.. – david 2013-12-09 09:29:24