Core Data in Swift

207 Pages·2016·8.453 MB·English

by  Zarra, Marcus S.

Early Praise for Core Data in Swift
Marcus’s books have long been my go-to recommendation for people who want
to learn about Core Data. With new information for beginners and experts alike,
they are a great insight into how you should be using Core Data and the features
that it offers.
➤ Daniel Tomlinson
Senior software engineer, Rocket Apps Ltd.
Marcus has a profound understanding of Core Data, and this book describes not
only the basics of working with Core Data, but also how to do so in a performant
manner, with explanations and examples. This is an indispensable reference,
alongside Apple’s documentation, and one that will quickly make Core Data your
go-to persistence mechanism. You’ll be able to deal with anything that comes up
with confidence.
➤ Abizer Nasir
Lead developer, Jungle Candy Software Ltd.
A compelling book, packed with useful information.
➤ Steven Oxley
Senior engineer, Social Native
We've left this page blank to
make the page numbers the
same in the electronic and
paper books.
We tried just leaving it out,
but then people wrote us to
ask about the missing pages.
Anyway, Eddy the Gerbil
wanted to say “hello.”
Core Data in Swift
Data Storage and Management for iOS and OS X
Marcus S. Zarra
The Pragmatic Bookshelf
Raleigh, North Carolina
Many of the designations used by manufacturers and sellers to distinguish their products
are claimed as trademarks. Where those designations appear in this book, and The Pragmatic
Programmers, LLC was aware of a trademark claim, the designations have been printed in
initial capital letters or in all capitals. The Pragmatic Starter Kit, The Pragmatic Programmer,
Pragmatic Programming, Pragmatic Bookshelf, PragProg and the linking g device are trade-
marks of The Pragmatic Programmers, LLC.
Every precaution was taken in the preparation of this book. However, the publisher assumes
no responsibility for errors or omissions, or for damages that may result from the use of
information (including program listings) contained herein.
Our Pragmatic books, screencasts, and audio books can help you and your team create
better software and have more fun. Visit us at https://pragprog.com.
The team that produced this book includes:
Jacquelyn Carter (editor)
Potomac Indexing, LLC (index)
Liz Welch (copyedit)
Gilson Graphics (layout)
Janet Furlow (producer)
For sales, volume licensing, and support, please contact [email protected].
For international rights, please contact [email protected].
Copyright © 2016 The Pragmatic Programmers, LLC.
All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted,
in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise,
without the prior consent of the publisher.
Printed in the United States of America.
ISBN-13: 978-1-68050-170-4
Encoded using the finest acid-free high-entropy binary digits.
Book version: P2.0—July 2016
Contents
Introduction . . . . . . . . . . . . . ix
1. Before We Begin . . . . . . . . . . . . 1
Test Application 1
The Storyboard 2
The Recipe List 4
The Recipe Detail 6
The Edit Workflow 7
Ready for Core Data 10
2. Under the Hood . . . . . . . . . . . . 13
Introducing the NSManagedObjectModel 15
Integrating with the NSPersistentStoreCoordinator 17
Adding the NSManagedObjectContext 20
Working with NSManagedObject Instances 21
Building an NSFetchRequest 28
NSSortDescriptor 31
Wrapping Up 32
3. iOS: NSFetchedResultsController . . . . . . . 33
How to Use the NSFetchedResultsController 33
Under the Hood of the NSFetchedResultsController 40
Building Our Own: MSZContextWatcher 42
Wrapping Up 45
4. Versioning and Migration . . . . . . . . . 47
Some Maintenance Before We Migrate 48
A Simple Migration 50
The Difference Between Light and Heavy Migrations 53
A Heavy/Manual Migration 54
Contents • vi
Fundamentals of Core Data Versioning 61
Wrapping Up 64
5. Performance Tuning . . . . . . . . . . . 65
Persistent Store Types 65
Optimizing Your Data Model 67
Fetching 71
Faulting 74
Access Patterns 77
Wrapping Up 78
6. Threading . . . . . . . . . . . . . 79
Threading and Core Data 80
Working on the Main Queue 81
Working off the Main Queue 83
Interqueue Communication 83
Parent/Child NSManagedObjectContext Design 86
Export Operation 87
Import Operation 93
Asynchronous Saving 98
Debug Concurrency Checking 101
Wrapping Up 102
7. Bulk Changes . . . . . . . . . . . . 103
Running with Scissors 103
Doing Bulk Updates 104
Notifying the Application of Changes 107
Bulk Deletes 109
Things to Consider When Using the Bulk Change APIs 110
Wrapping Up 111
8. Network Operations . . . . . . . . . . 113
The Problem and the Approach 113
The Solution 114
Accessing the Network Operations 121
Wrapping Up 121
9. Using Core Data with iCloud . . . . . . . . 123
Introducing the UIManagedDocument 124
Direct NSManagedObjectContext to iCloud 129
Consuming Changes from iCloud 132
Under the Hood 133
Contents • vii
Migrating an Existing Application 135
Desktop iCloud Integration 138
Issues with Data Quantities 140
Sharing Data Between iOS and OS X 140
Wrapping Up 142
10. Adding a Desktop Foundation . . . . . . . . 143
Our Application 143
Our Application Design 144
Sharing the Data Model 144
Building the Controller Layer 145
Building the User Interface 147
Adding a Splash of Code 152
Wrapping Up 155
11. Bindings, KVC, and KVO . . . . . . . . . 157
Key Value Coding 158
Key Value Observing 159
Cocoa Bindings and Core Data 161
Other Interface Elements That Use KVO, KVC, and Core Data 164
Wrapping Up 168
12. Spotlight, Quick Look, and Core Data . . . . . . 169
Integrating with Spotlight 170
Integrating with Quick Look 183
Putting It All Together 188
Wrapping Up 188
Index . . . . . . . . . . . . . . 191
Introduction
It’s amazing to realize that as of the writing of this book, Core Data is over
12 years old. That’s an incredible number when you consider that it’s more
powerful and more popular today than it has ever been. For a framework,
that’s pretty spectacular.
In this book we discuss Core Data and work with the framework from the
perspective of Swift. Swift is a young language and has a lot of growing yet
to do, but its popularity can’t be denied.
It’s clear that Swift is important to Apple and therefore should be equally
important to developers who work on Apple’s platforms.
Is This Book for You?
If you plan on writing an application that saves data to disk, then you should
take a very long look at Core Data. Whether you’re focusing on the desktop
or the iPhone, Core Data is the most efficient solution to data persistence.
A good way to confirm that you know enough Cocoa to benefit from this book
is to take a look at Chapter 1, Before We Begin, on page 1. You should find
it dense, but every step should be familiar to you.
What Is Core Data?
In the simplest terms, Core Data is an object graph that can be persisted to
disk. But just like describing a man as a “bag of mostly water,” that description
hardly does Core Data justice. If you have worked with Interface Builder
(specifically on OS X), you know that it effectively removes a third of the
coding from the Model-View-Controller (MVC) design pattern. With Interface
Builder, developers don’t need to spend countless hours writing and rewriting
their user interface to make sure that it’s pixel perfect. Instead, they simply
drag and drop the elements in the IDE, bind them together, and call it done.
report erratum • discuss