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@kenthumphries
Last active August 29, 2015 14:26
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Method to quickly perform a block using a temporary managed object context. Can be useful if you need to perform a few pre-migration optimisations to a database.
typedef NSError *(^NSManagedObjectContextBlock)(NSManagedObjectContext *context);
+ (void)performBlock:(NSManagedObjectContextBlock)block withTemporaryManagedObjectContextFromDatabaseAtURL:(NSURL *)url withModelBundle:(NSBundle *)bundle
{
NSParameterAssert(block);
if (!block)
{
return;
}
NSDictionary *storeMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:url error:nil];
NSManagedObjectModel *sourceModel = [NSManagedObjectModel mergedModelFromBundles:@[bundle] forStoreMetadata:storeMetadata];
if (sourceModel) // If sourceModel cannot be found, cannot create a context
{
@autoreleasepool {
// Create a temporary persistentStoreCoordinator based on source model
NSPersistentStoreCoordinator *temporaryStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:sourceModel];
NSError *error;
[temporaryStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:url
options:@{NSIgnorePersistentStoreVersioningOption:@YES}
error:&error];
if (!error)
{
NSManagedObjectContext *temporaryManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType: NSMainQueueConcurrencyType];
temporaryManagedObjectContext.persistentStoreCoordinator = temporaryStoreCoordinator;
block(temporaryManagedObjectContext);
temporaryManagedObjectContext = nil; // Clean up to release any ownership of DB store
}
temporaryStoreCoordinator = nil; // clean up to release any ownership of DB store
}
}
}
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