INTRODUCTIONINTRODUCTIONTO CORE DATATO CORE DATA

Orlando iOS Developer GroupOrlando iOS Developer Group01/23/201301/23/2013

AHTEN INDUSTRIESScott AhtenScott Ahten

Who Am I?Who Am I?

Scott Ahten, Ahten IndustriesScott Ahten, Ahten Industries

Technologist, iOS DeveloperTechnologist, iOS Developer

scott@ahtenindustries.comscott@ahtenindustries.com

Topics CoveredTopics Covered

What is Core Data?What is Core Data?

When should I use Core Data?When should I use Core Data?

Framework overviewFramework overview

Using Core DataUsing Core Data

MigrationsMigrations

Threading & concurrency typesThreading & concurrency types

What is Core DataWhat is Core Data

Not a Database!Not a Database!

Not an Object Relational Mapping frameworkNot an Object Relational Mapping framework

What is Core DataWhat is Core Data

Object Persistence FrameworkObject Persistence Framework

CRUD operationsCRUD operations

Queries using NSPredicateQueries using NSPredicate

Aggregate queriesAggregate queries

Multiple persistent storeMultiple persistent store

Available on iOS and Mac OS X DesktopAvailable on iOS and Mac OS X Desktop

Persistent Persistent Store TypesStore Types

BinaryBinary

In MemoryIn Memory

XML (Desktop Only)XML (Desktop Only)

SQLiteSQLite

Custom TypesCustom Types

Core Data vs. SQLiteCore Data vs. SQLite

SQLiteSQLite Core DataCore Data

Multiple UpdateMultiple Update YESYES NONO

Multiple DeleteMultiple Delete YESYES NONO

Auto Populate ObjectsAuto Populate Objects NONO YESYES

Custom SQLCustom SQL YESYES NONOAutomaticAutomatic

Lightweight MigrationsLightweight Migrations NONO YESYES

SpeedSpeed YESYES YESYES

Model ObjectsModel Objects NONO YESYES

When Should IWhen Should IUse CoreData?Use CoreData?

Wrong QuestionWrong Question

When Shouldn’t I use Core Data?When Shouldn’t I use Core Data?

Really Fast - Highly Optimized by AppleReally Fast - Highly Optimized by Apple

All but trivial and special casesAll but trivial and special cases

You should be using Model objectsYou should be using Model objects

Core Data and MVCCore Data and MVC

ControlleControllerr

ControlleControllerr

ViewViewViewView

ModelModelModelModel

Core DataCore Data

Model ObjectsModel Objects

NSManagedObject subclassNSManagedObject subclass

Lifecycle eventsLifecycle events

ValidationValidation

FaultingFaulting

Undo SupportUndo Support

RelationshipsRelationships

Core Data FrameworkCore Data Framework

ApplicationApplicationApplicationApplication

NSManagedObjectNSManagedObjectNSManagedObjectNSManagedObject

NSManageObjectContextNSManageObjectContextNSManageObjectContextNSManageObjectContext

NSPersistentStoreCoordinatorNSPersistentStoreCoordinatorNSPersistentStoreCoordinatorNSPersistentStoreCoordinator NSManageObjectModelNSManageObjectModelNSManageObjectModelNSManageObjectModel

NSPersistentStoreNSPersistentStoreNSPersistentStoreNSPersistentStore

XMLXMLXMLXML SQLiteSQLiteSQLiteSQLite BinaryBinaryBinaryBinary MemoryMemoryMemoryMemory CustomCustomCustomCustom

Core Data StackCore Data Stack

Setup in App DelegateSetup in App Delegate

Xcode Core Data templateXcode Core Data template

NSPersistentStoreCoordinatorNSPersistentStoreCoordinator

Coordinates access to one or more persistent Coordinates access to one or more persistent storesstores

Managed Object ModelManaged Object Model

Set store optionsSet store options

NSPersistentStoreCoordinatorNSPersistentStoreCoordinator

// 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:@"Example_App.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator;}

NSPersistentStoreCoordinatorNSPersistentStoreCoordinator

// 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:@"Example_App.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator;}

NSPersistentStoreCoordinatorNSPersistentStoreCoordinator

// 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:@"Example_App.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator;}

NSPersistentStoreCoordinatorNSPersistentStoreCoordinator

// 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:@"Example_App.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator;}

NSManagedObjectModelNSManagedObjectModel

Schema for ModelsSchema for Models

Entities, properties, relationships, etc.Entities, properties, relationships, etc.

ValidationsValidations

Fetch RequestsFetch Requests

ConfigurationsConfigurations

Objective-C SubclassObjective-C Subclass

NSManagedObjectModelNSManagedObjectModel

Attribute TypesAttribute Types

Integer TypesInteger Types

DecimalDecimal

DoubleDouble

FloatFloat

StringString

BooleanBoolean

DateDate

Binary DataBinary Data

Other Types?Other Types?

Serialize to NSData via NSCoderSerialize to NSData via NSCoder

Value Transformer and Transformable typeValue Transformer and Transformable type

Opaque to QueriesOpaque to Queries

NSManagedObject subclassNSManagedObject subclass

Attribute OptionsAttribute Options

TransientTransient

OptionalOptional

IndexedIndexed

Default ValuesDefault Values

Store in external record file (iOS 5 >=)Store in external record file (iOS 5 >=)

RelationshipsRelationships

NSSet, not NSArrayNSSet, not NSArray

One to oneOne to one

One to many and many to manyOne to many and many to many

Minimum and maximum countMinimum and maximum count

Ordered returned NSOrderedSet (iOS 5>=)Ordered returned NSOrderedSet (iOS 5>=)

Delete RulesDelete Rules

Nullify, Cascade, DenyNullify, Cascade, Deny

NSManagedObjectModelNSManagedObjectModel

// 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:@"Example_App" withExtension:@"momd"]; _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; return _managedObjectModel;}

NSManagedObjectModelNSManagedObjectModel

// 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:@"Example_App" withExtension:@"momd"]; _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; return _managedObjectModel;}

NSManagedObjectModelNSManagedObjectModel

// 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:@"Example_App" withExtension:@"momd"]; _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; return _managedObjectModel;}

NSManagedObjectContextNSManagedObjectContext

Scratch Pad for EntitiesScratch Pad for Entities

Queried objects are pulled into contextQueried objects are pulled into context

Can be FaultedCan be Faulted

Entities inserted into contextEntities inserted into context

Changes are not persisted until calling save:Changes are not persisted until calling save:

NSManagedObjectContextNSManagedObjectContext

Not thread safe!Not thread safe!

One context per thread One context per thread

More than one context per coordinatorMore than one context per coordinator

Merge notificationsMerge notifications

Concurrency Types (iOS 5>=)Concurrency Types (iOS 5>=)

Blocks, GCD queuesBlocks, GCD queues

NSManagedObjectContextNSManagedObjectContext

// 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;}

NSManagedObjectContextNSManagedObjectContext

// 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;}

SavingSaving

Save occurs per contextSave occurs per context

Saves changes to persistent storeSaves changes to persistent store

Should save on applicationWillTerminate:Should save on applicationWillTerminate:

Can be reset to discard changesCan be reset to discard changes

SavingSaving

- (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. } }}

NSManagedObjectNSManagedObject

Represents an entity in your modelRepresents an entity in your model

Superclass of managed object subclassesSuperclass of managed object subclasses

Access attributes via KVC/KVO and propertiesAccess attributes via KVC/KVO and properties

Pass NSManagedObjectIDs between threadsPass NSManagedObjectIDs between threads

Xcode can generate subclass with accessorsXcode can generate subclass with accessors

Can be a faultCan be a fault

Querying EntitesQuerying Entites

NSPredicateNSPredicate

Rich query syntaxRich query syntax

Aggregate property valuesAggregate property values

Compound predicatesCompound predicates

Queries can return faulted entities based on Queries can return faulted entities based on result typeresult type

Batch sizeBatch size

FaultsFaults

Only object IDOnly object ID

Performance & memoryPerformance & memory

Include specific propertiesInclude specific properties

Prefetch relationshipsPrefetch relationships

Querying EntitesQuerying Entites

NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];[request setSortDescriptors:sortDescriptors];

NSError *error = nil;NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];if (mutableFetchResults == nil) { // Handle the error.}

Querying EntitesQuerying Entites

NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];[request setSortDescriptors:sortDescriptors];

NSError *error = nil;NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];if (mutableFetchResults == nil) { // Handle the error.}

Querying EntitesQuerying Entites

NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];[request setSortDescriptors:sortDescriptors];

NSError *error = nil;NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];if (mutableFetchResults == nil) { // Handle the error.}

Querying EntitesQuerying Entites

NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];[request setSortDescriptors:sortDescriptors];

NSError *error = nil;NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];if (mutableFetchResults == nil) { // Handle the error.}

PredicatesPredicates

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(lastName like[cd] %@) AND (birthday > %@)",         lastNameSearchString, birthdaySearchDate];

NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"anAttribute == YES"];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"grade > %d", 7];

[fetchRequest setPredicate:predicate];

Inserting EntitiesInserting Entities

Insert into managed object contextInsert into managed object context

Entities are not yet persisted until context is Entities are not yet persisted until context is savedsaved

Inserting EntitiesInserting Entities

- (void)insertNewObject:(id)sender{ NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template. [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"]; // Save the context. NSError *error = nil; if (![context save:&error]) { // Replace this implementation with code to handle the error appropriately. }}

Inserting EntitiesInserting Entities

- (void)insertNewObject:(id)sender{ NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template. [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"]; // Save the context. NSError *error = nil; if (![context save:&error]) { // Replace this implementation with code to handle the error appropriately. }}

Inserting EntitiesInserting Entities

- (void)insertNewObject:(id)sender{ NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template. [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"]; // Save the context. NSError *error = nil; if (![context save:&error]) { // Replace this implementation with code to handle the error appropriately. }}

Inserting EntitiesInserting Entities

- (void)insertNewObject:(id)sender{ NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template. [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"]; // Save the context. NSError *error = nil; if (![context save:&error]) { // Replace this implementation with code to handle the error appropriately. }}

Deleting EntitesDeleting Entites

Entities are marked as deletedEntities are marked as deleted

No longer returned in queriesNo longer returned in queries

Not actually deleted until context is savedNot actually deleted until context is saved

Deletes can be discarded before save by Deletes can be discarded before save by discarding or resetting the contextdiscarding or resetting the context

Deleting EntitesDeleting Entites

- (void)deleteEvent:(NSManagedObject*)event{ NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

NSError *error = nil; [managedObjectContext deleteObject: event]; if (![managedObjectContext save:&error]) { // Replace this implementation with code to handle the error appropriately. }}

Updating EntitiesUpdating Entities

Same as insertSame as insert

Change properties and save contextChange properties and save context

Updates can be discarded before save by Updates can be discarded before save by discarding or resetting the contextdiscarding or resetting the context

MigrationsMigrations

Schemas changeSchemas change

Create new model version Create new model version

Automatic lightweight migrationAutomatic lightweight migration

Manual migrationManual migration

Not all changes require migrationNot all changes require migration

Validation, default values, Objective-C classValidation, default values, Objective-C class

Concurency TypesConcurency Types

iOS 5 >=iOS 5 >=

NSConfinementConcurrencyTypeNSConfinementConcurrencyType

Pre iOS 5 ConcurrencyPre iOS 5 Concurrency

NSPrivateQueueConcurrencyType NSPrivateQueueConcurrencyType

Private dispatch queuePrivate dispatch queue

NSMainQueueConcurrencyType NSMainQueueConcurrencyType

Main QueueMain Queue

ResourcesResources

Core Data Programming Guide Core Data Programming Guide http://developer.apple.com/library/mac/#http://developer.apple.com/library/mac/#documentation/cocoa/Conceptual/CoreData/cdProgrammingGuide.htmldocumentation/cocoa/Conceptual/CoreData/cdProgrammingGuide.html

Predicate Programming Guide Predicate Programming Guide http://developer.apple.com/library/mac/#http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/predicates.htmldocumentation/Cocoa/Conceptual/Predicates/predicates.html

Grand Central Dispatch (GCD)Grand Central Dispatch (GCD)http://developer.apple.com/library/ios/#http://developer.apple.com/library/ios/#documentation/Performance/Reference/GCD_libdispatch_Ref/Referencedocumentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html/reference.html

ResourcesResources

Magical RecordMagical Recordhttp://developer.apple.com/library/mac/#http://developer.apple.com/library/mac/#documentation/cocoa/Conceptual/CoreData/cdProgrammingGuide.htmldocumentation/cocoa/Conceptual/CoreData/cdProgrammingGuide.html

Multi-Context Core DataMulti-Context Core Datahttp://www.cocoanetics.com/2012/07/multi-context-coredata/http://www.cocoanetics.com/2012/07/multi-context-coredata/

Core Data EditorCore Data Editorhttp://christian-kienle.de/CoreDataEditorhttp://christian-kienle.de/CoreDataEditor

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