Core data lightweight_migration

Core Data
-Version & Migration
Michael Pan
13年8月15⽇日星期四

Migration
• Automatic (Lightweight) Migration
• Manual Migration

Lightweight migration can do
• Adding or removing an entity, attribute or relationship
• Make an attribute non-optional with a default value
• Making a non-optional attribute optional
• Renaming an entity or attribute using a renaming identiﬁer

Create master-detail application

Check Core Data

Run it

Select core data model

Add ModelVersion

Version name

ModifyVersion 2
Entity : Event => Record

Change the version

Run - Crash
Unresolved error Error Domain=NSCocoaErrorDomain Code=134100 "The operation couldn’t be completed. (Cocoa error
134100.)" UserInfo=0x834a9f0 {metadata={
NSPersistenceFrameworkVersion = 419;
NSStoreModelVersionHashes = {
Event = <5431c046 d30e7f32 c2cc8099 58add1e7 579ad104 a3aa8fc4 846e97d7 af01cc79>;
};
NSStoreModelVersionHashesVersion = 3;
NSStoreModelVersionIdentifiers = (
""
);
NSStoreType = SQLite;
NSStoreUUID = "E8AAA7FE-4F73-4D13-B7F2-451C0F487E21";
"_NSAutoVacuumLevel" = 2;
}, reason=The model used to open the store is incompatible with the one used to create the store}, {
metadata = {
NSPersistenceFrameworkVersion = 419;
NSStoreModelVersionHashes = {
Event = <5431c046 d30e7f32 c2cc8099 58add1e7 579ad104 a3aa8fc4 846e97d7 af01cc79>;
};
NSStoreModelVersionHashesVersion = 3;
NSStoreModelVersionIdentifiers = (
""
);
NSStoreType = SQLite;
NSStoreUUID = "E8AAA7FE-4F73-4D13-B7F2-451C0F487E21";
"_NSAutoVacuumLevel" = 2;
};
reason = "The model used to open the store is incompatible with the one used to create the store";
}

Enable auto migration
• AppDelegate.m
• - (NSPersistentStoreCoordinator *)persistentStoreCoordinator
NSMutableDictionary *options = [NSMutableDictionary dictionary];
[options setValue:@YES forKey:NSMigratePersistentStoresAutomaticallyOption];
[options setValue:@YES forKey:NSInferMappingModelAutomaticallyOption];
if (![_persistentStoreCoordinator
addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL
options:options error:&error]) {
// ignore...
}

Crash again
Terminating app due to uncaught exception
'NSInvalidArgumentException', reason:
'executeFetchRequest:error: A fetch request must
have an entity.'

Change Entity name
• MasterViewController.m
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Record"
inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// ignore ...
}

Run - ok

Delete all data ﬁrst
• remove original codes
• MasterViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
! // Do any additional setup after loading the view, typically from a nib.
self.navigationItem.leftBarButtonItem = self.editButtonItem;
// UIBarButtonItem *addButton = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self
action:@selector(insertNewObject:)];
// self.navigationItem.rightBarButtonItem = addButton;
}

Change display

Model v3
V3 V2

NewRecordViewController

Add NewViewController
@interface NewRecordViewController : UIViewController
@property (weak, nonatomic) IBOutlet UITextField *commentField;
@property (weak, nonatomic) IBOutlet UITextView *tagsView;
@property (strong) NSManagedObjectContext * context;
@end

- (IBAction)addNewRecord:(id)sender {
NSManagedObject * newRecord = [NSEntityDescription
insertNewObjectForEntityForName:@"Record" inManagedObjectContext:self.context];
self.recordComment = self.commentField.text;
[newRecord setValue:self.recordComment forKey:@"comment"];
[newRecord setValue:self.recordTags forKey:@"tags"];
NSError * error;
if (![self.context save:&error]) {
if (error) {
NSLog(@"Fail to create new record");
}
}else{
[self.navigationController popViewControllerAnimated:YES];
}
}
Add new record

Add tag

TagViewController.h
@protocol TagViewControllerDelegate;
@interface TagViewController : UITableViewController
@property (strong) NSManagedObjectContext * context;
@property (weak) id<TagViewControllerDelegate> delegate;
@end
@protocol TagViewControllerDelegate <NSObject>
-(void) tagView:(TagViewController *) tagView insertNewTag:(NSManagedObject *) tag;
@end

TagViewController.m
-(void) fetchAllTags{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Tag"
inManagedObjectContext:self.context];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name"
ascending:NO];
NSArray *sortDescriptors = @[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSError * error;
self.tags = [[self.context executeFetchRequest:fetchRequest error:&error]
mutableCopy];
if (error) {
NSLog(@"Can not fetch tags");
}
}

Add new tag
-(void) insertNewTag:(NSString *) tagName{
NSManagedObject * newTag = [NSEntityDescription
insertNewObjectForEntityForName:@"Tag" inManagedObjectContext:self.context];
[newTag setValue:tagName forKey:@"name"];
NSError * error;
if(![self.context save:&error]){
if (error) {
NSLog(@"Fail to create new tag");
}
}else{
[self.tags addObject:newTag];
[self.tableView reloadData];
}
}

Send tags to NewRecordViewController
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:
(NSIndexPath *)indexPath
{
if ([self.delegate respondsToSelector:@selector(tagView:insertNewTag:)]) {
[self.delegate tagView:self insertNewTag:self.tags[indexPath.row]];
}
}

Receive tags in NewRecordViewController
-(void) tagView:(TagViewController *)tagView insertNewTag:(NSManagedObject *)tag{
[self.recordTags addObject:tag];
NSSortDescriptor * sortDescriptor = [NSSortDescriptor
sortDescriptorWithKey:@"name" ascending:YES];
NSSet * nameSet = self.recordTags ;
NSArray * sortedArray = [nameSet
sortedArrayUsingDescriptors:@[sortDescriptor]];
self.tagsView.text = [NSString stringWithFormat:@"%@",[[sortedArray
valueForKey:@"name" ] componentsJoinedByString:@","]];
[self.navigationController popViewControllerAnimated:YES];
}

Demo - BookingApp

SQLite debug message

Delete some version
• Remove .xcdatamodeld (Remove Reference Only)
• Open project in the ﬁnder
• ﬁnd out .xcdatamodeld
• Right-click -> Show Package Contents
• Delete what you want to delete

Question

Core data lightweight_migration

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