Manual Core Data schema migration in -[NSPersistentDocument configurePersistentStoreCoordinatorForURL:ofType:...] without "document changed" error?
Manual Core Data schema migration in -[NSPersistentDocument configurePersistentStoreCoordinatorForURL:ofType:...] without "document changed" error?
- Subject: Manual Core Data schema migration in -[NSPersistentDocument configurePersistentStoreCoordinatorForURL:ofType:...] without "document changed" error?
- From: "Barry Wark" <email@hidden>
- Date: Mon, 15 Dec 2008 10:29:39 -0800
The data model for my Core Data document-based app (10.5 only) is in a
framework, so automatic schema upgrades using a Core Data mapping
model don't appear to work. It appears that the Core Data machinery
doesn't find the appropriate data models or mapping model when they
are not in the app's main bundle. So, instead of using the automatic
migration, I'm running a migration manually in
configurePersistentStoreCoordinatorForURL:ofType:... in my
NSPersistenDocument subclass (code below). I migrate the persistent
store to a temporary file and then overwrite the existing file if the
migration succeeds. The document then presents an error with the
message "This document's file has been changed by another application
since you opened or saved it." when I try to save. As others on this
list have pointed out, this is due to my modification of the
document's file "behind its back". I tried updating the document's
file modification date, as shown below, but I then get an error dialog
with the message "The location of the document "test.ovproj" cannot be
determined." when I try to save. I'm less sure of the reason for this
error, but trading one unnecessary message (in this case) for an other
isn't quite what I was going for.
Can anyone offer some guidance? Is there a way to manually upgrade the
schema for a document's persistent store without triggering one of
these (in _this_ case unnecessary) warnings?
thanks,
Barry
code for upgrading the data store in my subclasses
-configurePersistentStoreCoordinatorForURL:ofType:... :
if(upgradeNeeded) {
NSManagedObjectModel *sourceModel = [NSManagedObjectModel
mergedModelFromBundles:VUIModelBundles()
forStoreMetadata:meta];
if(sourceModel == nil) {
*error = [NSError errorWithDomain:VUIErrorDomain
code:VUICoreDataErrorCode localizedReason:BWLocalizedString(@"Unable
to find original data model for project.")];
return NO;
}
NSManagedObjectModel *destinationModel = [self managedObjectModel];
NSMigrationManager *migrationManager =
[[NSMigrationManager alloc] initWithSourceModel:sourceModel
destinationModel:destinationModel];
NSMappingModel *mappingModel = [NSMappingModel
mappingModelFromBundles:VUIModelBundles()
forSourceModel:sourceModel
destinationModel:destinationModel];
if(mappingModel == nil) {
*error = [NSError errorWithDomain:VUIErrorDomain
code:VUICoreDataErrorCode localizedReason:BWLocalizedString(@"Unable
to find mapping model to convert project to most recent project
format.")];
return NO;
}
@try {
//move file to backup
NSAssert([url isFileURL], @"store url is not a file URL");
NSString *tmpPath = [NSString tempFilePath];
id storeType = [meta objectForKey:NSStoreTypeKey];
if(![migrationManager migrateStoreFromURL:url
type:storeType
options:storeOptions
withMappingModel:mappingModel
toDestinationURL:[NSURL
fileURLWithPath:tmpPath]
destinationType:storeType
destinationOptions:storeOptions
error:error]) {
return NO;
} else {
//replace old with new
if(![[NSFileManager defaultManager]
removeItemAtPath:[url path] error:error] ||
![[NSFileManager defaultManager]
moveItemAtPath:tmpPath toPath:[url path] error:error]) {
return NO;
}
// update document file modification date to
prevent warning (#292)
NSDate *newModificationDate = [[[NSFileManager
defaultManager] fileAttributesAtPath:[url path] traverseLink:NO]
objectForKey:NSFileModificationDate];
[self setFileModificationDate:newModificationDate];
}
}
@finally {
[migrationManager release];
}
}
}
return [super configurePersistentStoreCoordinatorForURL:url
ofType:fileType modelConfiguration:configuration
storeOptions:storeOptions error:error];
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