Core data WIPJam workshop @ MWC'14

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Slides from my talk at WIPJam, MWC'14

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Core data WIPJam workshop @ MWC'14

  1. 1. Diego Freniche / http://www.freniche.com Core Data in 547 easy steps slide 1/373
  2. 2. Diego Freniche / @dfreniche / http://www.freniche.com Core Data Workshop
  3. 3. Diego Freniche: programmer & teacher • @dfreniche • Freelance Mobile developer: iOS/Android/BB10/ webOS/... • In a former life Java Certifications Collector: SCJP 1.5, SCJP 1.6, SCWCD 1.5, SCBCD 1.3 • Some languages: BASIC, PASCAL, C, C++, Delphi, COBOL, Clipper, Visual Basic, Java, JavaScript, Objective-C Hello, World!
  4. 4. Diego Freniche / http://www.freniche.com Core Data: developer’s first impression
  5. 5. Diego Freniche / http://www.freniche.com
  6. 6. Diego Freniche / @dfreniche / http://www.freniche.com Core Data Hello World!
  7. 7. Diego Freniche / @dfreniche / http://www.freniche.com That’s easy peasy
  8. 8. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Apple’s code ! - (void)saveContext { NSError *error = nil; NSManagedObjectContext *managedObjectContext = self.managedObjectContext; if (managedObjectContext != nil) { if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) { // Replace this implementation with code to handle the error appropriately. // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } } } !#pragma mark - Core Data stack !// Returns the managed object context for the application. // If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application. - (NSManagedObjectContext *)managedObjectContext { if (_managedObjectContext != nil) { return _managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { _managedObjectContext = [[NSManagedObjectContext alloc] init]; [_managedObjectContext setPersistentStoreCoordinator:coordinator]; } return _managedObjectContext; } !// Returns the managed object model for the application. // If the model doesn't already exist, it is created from the application's model. - (NSManagedObjectModel *)managedObjectModel { if (_managedObjectModel != nil) { return _managedObjectModel; } NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Test" withExtension:@"momd"]; _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; return _managedObjectModel; } !// Returns the persistent store coordinator for the application. // If the coordinator doesn't already exist, it is created and the application's store added to it. - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (_persistentStoreCoordinator != nil) { return _persistentStoreCoordinator; } NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Test.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. Typical reasons for an error here include: * The persistent store is not accessible; * The schema for the persistent store is incompatible with current managed object model. Check the error message to determine what the actual problem was. If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory. If you encounter schema incompatibility errors during development, you can reduce their frequency by: * Simply deleting the existing store: [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil] * Performing automatic lightweight migration by passing the following dictionary as the options parameter: @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES} Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator; } !#pragma mark - Application's Documents directory !// Returns the URL to the application's Documents directory. - (NSURL *)applicationDocumentsDirectory { return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; }
  9. 9. Diego Freniche / @dfreniche / http://www.freniche.com Corollary • Never, ever use the Core Data checkbox • BIG design flaws: • Core Data Stack coupled to AppDelegate: • can’t reuse in other projects • separations of concerns, anyone? • ugly! and just ONE Core Data Stack • They don’t even use a custom class
  10. 10. Diego Freniche / @dfreniche / http://www.freniche.com What is Core Data? • Poll • A Framework. Must be important: its name starts with “Core” • An ORM • The model of your App • Technology to help you that has a steep learning curve
  11. 11. Diego Freniche / @dfreniche / http://www.freniche.com One of the problems • Objet - Relational impedance • SQL: 70s/80s • OOP: 80s-
  12. 12. Diego Freniche / @dfreniche / http://www.freniche.com Exhibit 1: composition id name idCard Person +name: String +idCard: idCard +bankAccout: bankAccount idCard +number: int +letter: char +checkLetter() VARCHAR ¿?
  13. 13. Diego Freniche / @dfreniche / http://www.freniche.com Employee +empNumber: int Person +name: String +idCard: idCard Exhibit 2: inheritance Hyena Politician +moneyTaken: double
  14. 14. Diego Freniche / @dfreniche / http://www.freniche.com Exhibit 3: collection modelling Person +name: String +bills: Bill[] Bill 0..*1 http://en.wikipedia.org/wiki/First_normal_form
  15. 15. Diego Freniche / @dfreniche / http://www.freniche.com Relational World • tables • cartesian products • rows/ columns • normal forms • Objects • object collections • composition • inheritance OO World
  16. 16. Diego Freniche / @dfreniche / http://www.freniche.com The solution: ORM • Object Relational Mapper • Hibernate (Java, .Net) • Core Data (Cocoa) • Core Data is our model • can persist our objects in several ways
  17. 17. Diego Freniche / @dfreniche / http://www.freniche.com Which problems will Core Data help me solve? • Persist my data • Cache online data • to speed up things • to show something to the user when (if) there’s no Internet connection • Navigate the object graph: • [([Company allEmployees][0]).boss name]; • Maintain ViewControllers in sync
  18. 18. Diego Freniche / @dfreniche / http://www.freniche.com Don’t fight the Frameworks! • Yes! You need to learn them! • Everything well thought-out to work with Core Data • Working with databases without Core Data? • not so much fun! • reinvent the wheel • this is not JavaScript-Land!
  19. 19. Diego Freniche / @dfreniche / http://www.freniche.com Core Data terms • Entity • an entity in our model == Object in memory == row in table • Attribute • Relationship • Object graph http://ogre.berniecode.com/ogre_white_paper
  20. 20. Diego Freniche / @dfreniche / http://www.freniche.com To get the most out of Core Data • You need to understand: • KVC, KVO • ARC, memory management • delegate & MVC patterns • that singletons are evil (more or less)
  21. 21. Diego Freniche / @dfreniche / http://www.freniche.com The Core Data Stack Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model
  22. 22. Diego Freniche / @dfreniche / http://www.freniche.com Managed Object Context Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model
  23. 23. Diego Freniche / @dfreniche / http://www.freniche.com Our Model NSManagedObject NSManagedObject NSManagedObject NSManagedObject Persisted NSManagedObjectContext NSObject In memory only
  24. 24. Diego Freniche / @dfreniche / http://www.freniche.com Move away from NSObject! ! @interface  MyClass  :  NSObject   ! @end     ! @interface  MyClass  :  NSManagedObject   ! @end  
  25. 25. Diego Freniche / @dfreniche / http://www.freniche.com Managed Object Context: MOC • Managed Object Context: in-memory space where CD manages all our model’s objects. • All CRUD is done against a MOC. We persist data using [context save:] • Our model’s objects are Managed Objects. • The MOC needs a Persistent Store Coordinator to save the object graph in persistent store.
  26. 26. Diego Freniche / @dfreniche / http://www.freniche.com Managed Object Model Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model
  27. 27. Diego Freniche / @dfreniche / http://www.freniche.com Managed Object Model • Maps our model objects into database tables. • Objects == NSManagedObject • Classes == NSEntityDescription • We describe our App entities inside a MOM • stored inside .xcdatamodeld files in Xcode. Compiles into .momd • graphic editor / class generator (dumb)
  28. 28. Diego Freniche / @dfreniche / http://www.freniche.com Managed Object Model Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model
  29. 29. Diego Freniche / @dfreniche / http://www.freniche.com Persistent Store Coordinador Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model Makes the mapping between our App’s objects and the physical storage inside the Persistent Object Store. 99% time we’ll work with ONE Object Store, but it’s possible use more than one. For example, a sqlite DB with recipes and another DB with notes, stars, etc. Coordinator: single façade to work with different Stores. ! A managed object context can then create an object graph based on the union of all the data stores the coordinator covers Persistent Object Store
  30. 30. Diego Freniche / http://www.freniche.com Persistent Store Coordinador Called Coordinator for a reason: serializes operations ! Core Data API is NOT Thread safe ! Persistent Store Coordinator makes it Thread Safe Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model Managed Object Context Managed Object Context
  31. 31. Diego Freniche / @dfreniche / http://www.freniche.com Persistent Object Store Managed Object Context Persistent Store Coordinator Persistent Object Store Managed Object Model NSXMLStoreType (XML only OS X, bad performance)! NSSQLiteStoreType (partial object graph in memory)! NSBinaryStoreType (kind of NIBs, poor performance)! NSInMemoryStoreType (good for testing) Makes the mapping between our App’s objects and the physical storage inside the Persistent Object Store. Supported Store Types
  32. 32. Diego Freniche / @dfreniche / http://www.freniche.com Creating the Core Data Stack ! -(void)setUpCoreDataStack { NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:[NSBundle allBundles]]; NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model]; ! NSURL *url = [[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject] URLByAppendingPathComponent:@"Database.sqlite"]; ! NSDictionary *options = @{NSPersistentStoreFileProtectionKey: NSFileProtectionComplete, NSMigratePersistentStoresAutomaticallyOption:@YES}; NSError *error = nil; NSPersistentStore *store = [psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:options error:&error]; if (!store) { NSLog(@"Error adding persistent store. Error %@",error); ! NSError *deleteError = nil; if ([[NSFileManager defaultManager] removeItemAtURL:url error:&deleteError]) { error = nil; store = [psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:options error:&error]; } ! if (!store) { // Also inform the user... NSLog(@"Failed to create persistent store. Error %@. Delete error %@",error,deleteError); abort(); } } ! self.managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType]; self.managedObjectContext.persistentStoreCoordinator = psc; } ! // http://commandshift.co.uk/blog/2013/09/07/the-core-data-stack/
  33. 33. Diego Freniche / http://www.freniche.com DF Core Data Stack Warning: really bad code ahead!
  34. 34. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Dependency injection? Or singletons FTW? • It depends :-)
  35. 35. Diego Freniche / http://www.freniche.com To create a Core Data Project • Link against Core Data Framework • Write some code to create a Core Data Stack • Test it! In memory (better)
  36. 36. Diego Freniche / @dfreniche / http://www.freniche.com SQL in SQLite • http://sqlite.org/lang.html • We can have a look at generated SQL: • -com.apple.CoreData.SQLDebug 1 • Schemes > Edit Scheme > Test > Arguments
  37. 37. Diego Freniche / @dfreniche / http://www.freniche.com 1 2 3
  38. 38. Diego Freniche / @dfreniche / http://www.freniche.com Accessing SQLite sqlitestudio.pl Look for your databases in: ! /Users/<usuario>/Library/Application Support/iPhone Simulator/<versión>/ Applications/<ID App>/Documents/ <archivo SQLite>
  39. 39. Diego Freniche / @dfreniche / http://www.freniche.com DDL: Data Definition Language • CREATE DATABASE, CREATE TABLE, CREATE INDEX, ALTER TABLE, DROP INDEX, ... • All written by Core Data • We DO NOT have to create anything: neither tables nor database • If we make changes, Core Data alters tables, columns, indexes...
  40. 40. Diego Freniche / @dfreniche / http://www.freniche.com Modelling We need a Data Model file to “draw” our model 1st, create all our model’s entities, then add attributes! ! Can subclass NSManagedObject to use compiler- time name checking, Xcode’s autofill,...
  41. 41. Diego Freniche / @dfreniche / http://www.freniche.com Modelling • New model versions: Editor > Add Model Version • Model (.xcdatamodeld) is a folder • Last version has no number. Oldest with higher number. WTF, Apple! (WTF: What a Tricky Fact) • 1st time we access model it creates persintent store lazily Select THIS
  42. 42. Diego Freniche / @dfreniche / http://www.freniche.com Versioning and changes • Activate always lightweight migration • If we make changes to the model, not changing version, version used in the model and version used to create DB doesn’t match: delete DB. • Reseting Content and Settings.. in Simulator • delete (by hand) .sqlite file
  43. 43. Diego Freniche / @dfreniche / http://www.freniche.com NSManagedObject NSManagedObject NSManagedObjectContext NSEntityDescription
  44. 44. Diego Freniche / @dfreniche / http://www.freniche.com NSManagedObject • base class implementing all “basic” object model behavior • We can NOT use Core Data with NSObject, we HAVE TO use NSManagedObject • Our model classes inherit from NSManagedObject • not mandatory, but... • allows us to add logic, use @property, get notifications... • have to be properly configured
  45. 45. Diego Freniche / @dfreniche / http://www.freniche.com Entities Design • Always add an order field • Try to create a good UML diagram at first • Yes, I’ve said UML! • Have an NSString constant with every Entity’s name inside .h
  46. 46. Diego Freniche / @dfreniche / http://www.freniche.com Extend NSManagedObject • Editor > Create NSManagedObject subclass... • creates @dynamic properties • getter / setter generated in runtime (@property in compile time) • Core Data doesn’t know at compile time if the persistent store is going to be XML or a DB (or in-memory)
  47. 47. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Entities Design Tips • Always add field order • Try to create a good UML diagram at first • Have an NSString constant with every Entity’s name inside .h
  48. 48. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Extend NSManagedObject • Editor > Create NSManagedObject subclass... • creates @dynamic properties • getter / setter generated in runtime (@property in compile time) • Core Data doesn’t know at compile time if the persistent store is going to be XML or a DB (or in-memory)
  49. 49. Diego Freniche / @dfreniche / http://www.freniche.com Extend NSManagedObject • overwrite init to call designated initializer ! -(id)init { NSManagedObjectContext *context = [[CoreDataStack coreDataStack] managedObjectContext]; return [self initWithEntity:[NSEntityDescription entityForName:kRETROITEM_ENTITY inManagedObjectContext:context ] insertIntoManagedObjectContext:context]; }
  50. 50. Diego Freniche / @dfreniche / http://www.freniche.com Validate Properties • One for every property, if we want it • Passing parameter by reference • It should return YES if validation is passed ! -(BOOL)validateName:(id *)ioValue error:(NSError * __autoreleasing *)outError;
  51. 51. Diego Freniche / @dfreniche / http://www.freniche.com Validator for operations • First thing: must call [super ...] • Useful to check business rules (using several properties) ! - (BOOL)validateForDelete:(NSError **)error - (BOOL)validateForInsert:(NSError **)error - (BOOL)validateForUpdate:(NSError **)error
  52. 52. Diego Freniche / @dfreniche / http://www.freniche.com Support for KVO • Good for Faults ! - (void)willAccessValueForKey:(NSString *)key
  53. 53. Diego Freniche / @dfreniche / http://www.freniche.com Inserting Entities (INSERT INTO) ! // using NSEntityDescription. Pass: entity name and context [NSEntityDescription insertNewObjectForEntityForName:@”RetroItems” inManagedObjectContext:context]; [retroItem setValue:@"Spectrum 48K" forKey:@"name"]; [retroItem setValue:@100.00 forKey:@"acquisitionCost"]; [retroItem setValue:[NSDate new] forKey:@"dateAcquired"]; insertNewObjectForEntityForName context save Context
  54. 54. Diego Freniche / @dfreniche / http://www.freniche.com Fetching entities (SELECT) • Query with NSFetchRequest • SELECT by definition is unordered • At least we need to provide • entity • order by
  55. 55. Diego Freniche / @dfreniche / http://www.freniche.com Step by Step fetch (Select) ! NSManagedObjectContext *context = [[CoreDataStack coreDataStack] managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:kRETRO_ITEM_ENTITY inManagedObjectContext:context]; [fetchRequest setEntity:entity]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO]; [fetchRequest setSortDescriptors:@[sortDescriptor]]; NSError *error = nil; NSArray *distincResults = [context executeFetchRequest:fetchRequest error:&error]; 1 2 3 4 5 6
  56. 56. Diego Freniche / @dfreniche / http://www.freniche.com Order querys NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"fecha_max" ascending:YES]; NSManagedObject returned inside NSArray are unordered unless otherwise we provide NSSortDescription. ! 1st, we create the sort descriptor [request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]]; Then we add to our NSFetchRequest the sort descriptors array:
  57. 57. Diego Freniche / @dfreniche / http://www.freniche.com Filtering querys NSManagedObjectContext *moc = [self managedObjectContext];! ! NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Employee" inManagedObjectContext:moc];! ! NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];! [request setEntity:entityDescription];! ! NSNumber *minimumSalary = ...;! ! NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(lastName LIKE[c] 'Worsley') AND (salary > %@)", minimumSalary];! ! [request setPredicate:predicate];! ! NSError *error = nil;! ! NSArray *array = [moc executeFetchRequest:request error:&error];! NSFetchRequest returns an array of NSManagedObject. We can use a NSPredicate to filter. ! Filter/NSPredicate acts here as the SQL WHERE clause. ! We need to add that query with setPredicate.
  58. 58. Diego Freniche / @dfreniche / http://www.freniche.com • CONTAINS: to query for strings that contain substrings. • ==: equality operator. • BEGINSWITH: a pre-made regular expression that looks for matches at the beginning of a string. • MATCHES: regular expression-like search. • ENDSWITH: opposite of BEGINSWITH. • <, >: less than and greater than.
  59. 59. Diego Freniche / @dfreniche / http://www.freniche.com Delete Entities (DELETE) + (void)deleteInstancesForEntityName:(NSString *)entityName inContext:(NSManagedObjectContext *)context { ! NSFetchRequest *fetch = [[NSFetchRequest alloc] init]; ! [fetch setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:context]]; NSError *error = nil; NSArray *dataObjects = [context executeFetchRequest:fetch error:&error]; for (NSManagedObject *dataObject in dataObjects) { [context deleteObject:dataObject]; } ! NSError *saveError = nil; [context save:&saveError]; }
  60. 60. Diego Freniche / @dfreniche / http://www.freniche.com Object identificator ! NSManagedObjectID *moID = [managedObject objectID]; ! -(NSManagedObject *)existingObjectWithID:(NSManagedObjectID *)objectID error:(NSError **)error
  61. 61. Diego Freniche / @dfreniche / http://www.freniche.com Accessing Properties Sometimes we don’t want the whole object (NSManagedObject) only the value of a property applying a function (max, min, etc.). NSFetchRequest *request = [[NSFetchRequest alloc] init];! ! NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:context];! ! [request setEntity:entity]; 1. Create NSFetchRequest as usual [request setResultType:NSDictionaryResultType]; 2. Tell NSFetchRequest to return NSDictionary instead NSArray: NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"creationDate"];! ! NSExpression *minExpression = [NSExpression expressionForFunction:@"min:" arguments:[NSArray arrayWithObject:keyPathExpression]]; 3. Define the field to calc upon (NSExpression), then the function
  62. 62. Diego Freniche / @dfreniche / http://www.freniche.com Accessing Properties NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];! ! [expressionDescription setName:@"minDate"];! ! [expressionDescription setExpression:minExpression];! ! [expressionDescription setExpressionResultType:NSDateAttributeType]; 4. Create a NSExpressionDescription: [request setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]];! ! NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error]; 5. Set in the query the properties to fetch if ([objects count] > 0) {! NSLog(@"Minimum date: %@", [[objects objectAtIndex:0] valueForKey:@"minDate"]);! } 6. Access our result:
  63. 63. Diego Freniche / @dfreniche / http://www.freniche.com Using Blocks to Sort If Sorting is not trivial maybe NSSortDescription is not enough. [[NSSortDescriptor alloc] initWithKey:<#(NSString *)#> ascending:<#(BOOL)#> comparator:<#^NSComparisonResult(id obj1, id obj2)cmptr#> ^(id a, id b) { NSNumber *lat1 = [[a valueForKey:@"latitude"] doubleValue]; NSNumber *lon1 = [a valueForKey:@"longitude"] doubleValue]; CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:lat1 longitude:lon1]; NSNumber *lat2 = [[b valueForKey:@"latitude"] doubleValue]; NSNumber *lon2 = [b valueForKey:@"longitude"] doubleValue]; CLLocation *loc2 = [[CLLocation alloc] initWithLatitude:lat2 longitude:lon2]; CLLocationDistance dist_a= [loc1 distanceFromLocation:locUser]; CLLocationDistance dist_b= [loc2 distanceFromLocation:locUser]; if ( dist_a < dist_b ) { return (NSComparisonResult)NSOrderedAscending; } else if ( dist_a > dist_b) { return (NSComparisonResult)NSOrderedDescending; } else { return (NSComparisonResult)NSOrderedSame; } }]; Ejemplo de ordenación de distancias:
  64. 64. Diego Freniche / @dfreniche / http://www.freniche.com Relationship example NSManagedObjectContext *context = [self managedObjectContext];! ! NSManagedObject *failedBankInfo = [NSEntityDescription! insertNewObjectForEntityForName:@"FailedBankInfo"! inManagedObjectContext:context];! ! [failedBankInfo setValue:@"Test Bank" forKey:@"name"];! [failedBankInfo setValue:@"Testville" forKey:@"city"];! [failedBankInfo setValue:@"Testland" forKey:@"state"];! ! NSManagedObject *failedBankDetails = [NSEntityDescription! insertNewObjectForEntityForName:@"FailedBankDetails"! inManagedObjectContext:context];! ! [failedBankDetails setValue:[NSDate date] forKey:@"closeDate"];! [failedBankDetails setValue:[NSDate date] forKey:@"updateDate"];! [failedBankDetails setValue:[NSNumber numberWithInt:12345] forKey:@"zip"];! [failedBankDetails setValue:failedBankInfo forKey:@"info"];! ! [failedBankInfo setValue:failedBankDetails forKey:@"details"];! ! NSError *error;! ! if (![context save:&amp;error]) {! NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);! }! Writing
  65. 65. Diego Freniche / @dfreniche / http://www.freniche.com Relationship example NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];! ! NSEntityDescription *entity = [NSEntityDescription! entityForName:@"FailedBankInfo" inManagedObjectContext:context];! ! [fetchRequest setEntity:entity];! ! NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];! ! for (NSManagedObject *info in fetchedObjects) {! ! NSLog(@"Name: %@", [info valueForKey:@"name"]);! ! NSManagedObject *details = [info valueForKey:@"details"];! NSLog(@"Zip: %@", [details valueForKey:@"zip"]);! }! Reading
  66. 66. Diego Freniche / @dfreniche / http://www.freniche.com NSFetchedResultsController • Controller without interface • Purpose: “feed” with data an UITableView • Protocol NSFetchedResultsControllerDelegate • section “Typical Use”: there’s the code found in template • connected to a Context: if there are changes of any object inside that context it receives a notification and updates automatically
  67. 67. Diego Freniche / @dfreniche / http://www.freniche.com NSFetchedResultsController Context NSManagedObject NSManagedObject NSManagedObject SQLite UITableView NSFetchedResultsController ??? delegate
  68. 68. Diego Freniche / @dfreniche / http://www.freniche.com All needed code for NSFetchedResults Cont. • In the Apple Docs!
  69. 69. Diego Freniche / http://www.freniche.com Idea: use Mogenerator
  70. 70. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Mogenerator created by Jonathan 'Wolf' Rentzsch
  71. 71. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Mogenerator (quoting from the web page) • http://rentzsch.github.io/mogenerator/ • generates Objective-C code for your Core Data custom classes • Unlike Xcode, mogenerator manages two classes per entity: one for machines, one for humans • The machine class can always be overwritten to match the data model, with humans’ work effortlessly preserved
  72. 72. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Installing mogenerator
  73. 73. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Two classes • _MyClass.*: machine generated • *MyClass.*: human edited ! • Never, ever recreate the classes again from the Core Data Model
  74. 74. Diego Freniche / http://www.freniche.com #import "_RetroItem.h" ! @interface RetroItem : _RetroItem {} // Custom logic goes here. @end #import "RetroItem.h" ! ! @interface RetroItem () ! // Private interface goes here. ! @end ! ! @implementation RetroItem ! // Custom logic goes here. ! @end Two classes
  75. 75. Diego Freniche / http://www.freniche.comDiego Freniche / @dfreniche / http://www.freniche.com Using it • it’s a script, so we can launch it from command line • using iTerm, DTerm, etc. • Best way: to have it inside our project • Create a new Aggregate Target (New Target > Other > Aggregate) • Add Build Phase > Add Run Script ! mogenerator --template-var arc=true -m RetroStuffTracker/ RetroStuffTracker.xcdatamodeld/RetroStuffTracker.xcdatamodel/
  76. 76. Diego Freniche / http://www.freniche.com
  77. 77. Diego Freniche / http://www.freniche.com Idea: use Magical Record
  78. 78. Diego Freniche / http://www.freniche.com Magical Record Demo Warning: really bad code ahead!
  79. 79. Diego Freniche / http://www.freniche.com Magical record != avoid Core Data at all costs • Just a bunch of categories to help you write less code • You have to know your sh*t • CocoaPods friendly • Ideal: use Unit testing + Mogenerator + CocoaPods + Magical Record • My point: 7 people, 7 ideas, all great • all different
  80. 80. Diego Freniche / http://www.freniche.com Idea: using asserts to check threads
  81. 81. Diego Freniche / http://www.freniche.com Asserts • Check if we are running UI code in the UI Thread • Check if we are NOT running Core Data code in the UI Thread ! #ifndef  CDHelloWord_DFThreadAsserts_h   #define  CDHelloWord_DFThreadAsserts_h   ! #define  DF_ASSERT_MAIN_THREAD  [NSThread  isMainThread]?:(NSLog(@"NOT  IN  MAIN  THREAD"),abort())   #define  DF_ASSERT_NOT_MAIN_THREAD  ![NSThread  isMainThread]?:(NSLog(@"IN  MAIN  THREAD,  BUT  NOT  EXPECTED"),abort())   ! ! #endif  
  82. 82. Diego Freniche / http://www.freniche.com Idea: create a common UITableView/Core data class
  83. 83. Questions?
  84. 84. Diego Freniche / @dfreniche / http://www.freniche.com Attributions • http://www.flickr.com/photos/paldies/85684217/ • http://www.flickr.com/photos/56380734@N05/6808753611/ • http://www.flickr.com/photos/msimdottv/4339697089/ • http://www.flickr.com/photos/mobilestreetlife/4179063482/ • http://www.flickr.com/photos/owldreams/4428782193/ • http://www.flickr.com/photos/miss_pupik/73160522/ • http://kfannerd713.deviantart.com/art/UNICORN-PUKING-RAINBOWS-WHAAAA-152117816 • http://www.flickr.com/photos/wwworks/4759535950/ • http://www.flickr.com/photos/barto/28135419/sizes/l/in/photolist-3ucFr-7aiwZ-aqWUu-bLebi-cDeVC-jt2YW-jWW1t-kQ25f-m86XP-swafK-yHMbE-yHMcc-yHMda-

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