Core data basic Workshop slides NSSpain 2013

Diego Freniche / @dfreniche / http://www.freniche.com

Core Data Workshop

http://www.freniche.com


Diego Freniche: programmer & teacher

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!

Before we start...

Before we start...

• Switch OFF phones

Before we start...


• Been here is funny

Before we start...



• ¡Live the moment!¡Carpe diem!

Before we start...



• ¡Live the moment!¡Carpe diem!

• Ask me a lot. Don’t yawn

Our objective: BUILD things

What you need (checklist)

• a Mac with OS X capable of running Xcode 4.6.1

• last Xcode 4 installed 4.6.1

• You can also use prerelease software, if you are a registered Apple developer. No support then, sorry :-D

• SimPholders installed: http://simpholders.com

• SQLLite database browser: http://sqlitebrowser.sourceforge.net

• (optional) set $HOME/Library folder visible, using (from a Terminal)

http://simpholders.com

http://simpholders.com

http://sqlitebrowser.sourceforge.net

http://sqlitebrowser.sourceforge.net

Diego Freniche / http://www.freniche.com

Core Data: developer’s first impression




Core Data in 547 easy steps slide 6/320




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






To get the most out of Core Data

• KVC, KVO

• ARC, memory management

• delegate & MVC patterns

• singletons are evil (more or less)




Core Data Hello World!




The Problem

• Objet - Relational impedance

• SQL: 70s/80s

• OOP: 80s-




Exhibit 1: composition

Person+name: String

+idCard: idCard

+bankAccout: bankAccount





Person+name: String

+idCard: idCard


idCard

+number: int+letter: char

+checkLetter()





id name idCardPerson

+name: String

+idCard: idCard


idCard


+checkLetter()






+name: String

+idCard: idCard


idCard


+checkLetter()

VARCHAR






+name: String

+idCard: idCard


idCard


+checkLetter()

VARCHAR ¿?




Employee

+empNumber: int

Person

+name: String+idCard: idCard

Exhibit 2: inheritance




Employee

+empNumber: int

Person



Politician

+moneyTaken: double




Employee

+empNumber: int

Person



Hyena

Politician

+moneyTaken: double




Exhibit 3: collection modelling

Person

+name: String

+bills: Bill[]

Bill

0..*1

http://en.wikipedia.org/wiki/First_normal_form






Relational World

• tables

• cartesian products

• rows/ columns

• normal forms

• Objects

• object collections

• composition

• inheritance

OO World




The solution: ORM

• Object Relational Mapper

• Hibernate (Java, .Net)

• Core Data (Cocoa)

• Core Data is our model

• can persist our objects in several ways




The Core Data Stack

Managed Object Context

Persistent Store Coordinator

Persistent Object Store

Managed Object Model




Our Model

NSManagedObjectContext

NSManagedObject

NSManagedObject

NSManagedObject

NSManagedObject

NSObject

PersistedIn memory only




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 save:

• Our model’s objects are Managed Objects.

• The MOC needs a Persistent Store Coordinator to save the object graph in persistent store.





• 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)




Persistent Store Coordinador





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

Coordinator: serializes operations








Managed Object ModelNSXMLStoreType (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




SQL in SQLite

• http://sqlite.org/lang.html

• We can see generated SQL: -com.apple.CoreData.SQLDebug 1

• Schemes > Edit Scheme > Test > Arguments



http://sqlite.org/lang.html

http://sqlite.org/lang.html


1

2

3




Accessing SQLite

sqlitebrowser.sourceforge.net

Look in:

/Users/<usuario>/Library/Application Support/iPhone Simulator/<versión>/Applications/<ID App>/Documents/<archivo SQLite>




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...




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,...




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




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




NSManagedObject

NSManagedObject

NSManagedObjectContext

NSEntityDescription




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




Entities Design

• Always add field order

• Try to create a good UML diagram at first

• Have an NSString constant with every Entity’s name inside .h




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)





• overwrite init to call designated initializer





• overwrite init to call designated initializer

-(id)init {

NSManagedObjectContext *context = [[CoreDataStack coreDataStack] managedObjectContext];

return [self initWithEntity:[NSEntityDescription entityForName:kRETROITEM_ENTITY inManagedObjectContext:context ] insertIntoManagedObjectContext:context];

}




Validate Properties

• One for every property, if we want it

• Passing parameter by reference

• It should return YES if validation is passed




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;




Validator for operations

• First thing: must call [super ...]

• Useful to check business rules (using several properties)




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




Support for KVO

• Good for Faults




Support for KVO

• Good for Faults

- (void)willAccessValueForKey:(NSString *)key




Inserting Entities (INSERT INTO)

insertNewObjectForEntityForName context save

Context




Inserting Entities (INSERT INTO)

// using NSEntityDescription. Pass: entity name and context

[NSEntityDescription insertNewObjectForEntityForName:@”MyEntity” inManagedObjectContext:context];

[retroItem setValue:@"Spectrum 48K" forKey:@"name"];

[retroItem setValue:@100.00 forKey:@"acquisitionCost"];

[retroItem setValue:[NSDate new] forKey:@"dateAcquired"];

insertNewObjectForEntityForName context save

Context




Fetching entities (SELECT)

• Query with NSFetchRequest

• SELECT by definition is unordered

• At least we need to provide

• entity

• order by




Step by Step fetch (Select)

1

2

3

4

5

6




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




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:




Filtering querysNSManagedObjectContext *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.




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];}




Object identificator




Object identificator

NSManagedObjectID *moID = [managedObject objectID];

-(NSManagedObject *)existingObjectWithID:(NSManagedObjectID *)objectID

error:(NSError **)error




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




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:




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:&error]) { NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);}

Escritura



http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObjectContext_Class/

http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObjectContext_Class/

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSError_Class/

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSError_Class/


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"]);}

Read



http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSFetchRequest_Class/




http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSEntityDescription_Class/




http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/

http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObject_Class/

http://developer.apple.com/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObject_Class/


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





SQLite

UITableView





SQLite

UITableView

???





Context

NSManagedObject

NSManagedObject

NSManagedObject

SQLite

UITableView

???





Context

NSManagedObject

NSManagedObject

NSManagedObject

SQLite

UITableView NSFetchedResultsController

???

delegate





Context

NSManagedObject

NSManagedObject

NSManagedObject

SQLite

UITableView NSFetchedResultsController

delegate




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-



http://www.flickr.com/photos/paldies/85684217/

http://www.flickr.com/photos/paldies/85684217/

http://www.flickr.com/photos/56380734@N05/6808753611/

http://www.flickr.com/photos/56380734@N05/6808753611/

http://www.flickr.com/photos/msimdottv/4339697089/

http://www.flickr.com/photos/msimdottv/4339697089/

http://www.flickr.com/photos/mobilestreetlife/4179063482/

http://www.flickr.com/photos/mobilestreetlife/4179063482/

http://www.flickr.com/photos/owldreams/4428782193/

http://www.flickr.com/photos/owldreams/4428782193/

http://www.flickr.com/photos/miss_pupik/73160522/

http://www.flickr.com/photos/miss_pupik/73160522/

http://kfannerd713.deviantart.com/art/UNICORN-PUKING-RAINBOWS-WHAAAA-152117816

http://kfannerd713.deviantart.com/art/UNICORN-PUKING-RAINBOWS-WHAAAA-152117816

http://www.flickr.com/photos/wwworks/4759535950/

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-yHMdH-yHMet-yHMff-DN6jZ-N8FeA-2DWGDT-2GeiTm-39i21d-4bhpGt-4jGHyr-4m9rnh-4prpxC-4zEAcX-4ANyKQ-4SMeBb-4UVPY4-4YhYGy-4YvSPE-5f8rXz-5fcQ1S-5iadPV-5EZwEn-5WwGLy-65JURT-6ix7Dz-6zWX7S-6Aw9Uw-6S6MQg-6XBNtR-6ZFjzY-73oC23-7dKvi6-7ue7o8-7uKomt-7xfEXb-bU9r8t-b1R7yg-b2bPp4/

http://www.flickr.com/photos/barto/28135419/sizes/l/in/photolist-3ucFr-7aiwZ-aqWUu-bLebi-cDeVC-jt2YW-jWW1t-kQ25f-m86XP-swafK-yHMbE-yHMcc-yHMda-yHMdH-yHMet-yHMff-DN6jZ-N8FeA-2DWGDT-2GeiTm-39i21d-4bhpGt-4jGHyr-4m9rnh-4prpxC-4zEAcX-4ANyKQ-4SMeBb-4UVPY4-4YhYGy-4YvSPE-5f8rXz-5fcQ1S-5iadPV-5EZwEn-5WwGLy-65JURT-6ix7Dz-6zWX7S-6Aw9Uw-6S6MQg-6XBNtR-6ZFjzY-73oC23-7dKvi6-7ue7o8-7uKomt-7xfEXb-bU9r8t-b1R7yg-b2bPp4/

Core data basic Workshop slides NSSpain 2013

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Transcript of Core data basic Workshop slides NSSpain 2013