iOS Recipes: Tips and Tricks for Awesome iPhone and iPad Apps

193 Pages·2011·2.64 MB·English

by  Matt Drance

Prepared exclusively for Mary Smithson
Beta
Book
Agile publishing for agile developers
Under Construction The book you’re reading is still under develop-
ment. As part of our Beta book program, we’re releasing this copy well
before a normal book would be released. That way you’re able to get
this content a couple of months before it’s available in finished form,
and we’ll get feedback to make the book even better. The idea is that
everyone wins!
Be warned. The book has not had a full technical edit, so it will con-
tain errors. It has not been copyedited, so it will be full of typos and
other weirdness. And there’s been no effort spent doing layout, so
you’ll find bad page breaks, over-long lines with little black rectan-
gles, incorrect hyphenations, and all the other ugly things that you
wouldn’t expect to see in a finished book. We can’t be held liable if you
use this book to try to create a spiffy application and you somehow
end up with a strangely shaped farm implement instead. Despite all
this, we think you’ll enjoy it!
Download Updates Throughout this process you’ll be able to down-
load updated ebooks from your account on http://pragprog.com. When
the book is finally ready, you’ll get the final version (and subsequent
updates) from the same address.
Send us your feedback In the meantime, we’d appreciate you sending
us your feedback on this book at http://pragprog.com/titles/cdirec/errata,
or by using the links at the bottom of each page.
Thank you for being part of the Pragmatic community!
Dave & Andy
Prepared exclusively for Mary Smithson
iOS Recipes
Tips and Tricks for Awesome iPhone and iPad Apps
Matt Drance
Paul Warren
The Pragmatic Bookshelf
Raleigh,NorthCarolina Dallas,Texas
Prepared exclusively for Mary Smithson
Many of the designations used by manufacturers and sellers to distinguish their prod-
uctsareclaimedastrademarks.Wherethosedesignationsappearinthisbook,andThe
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
PragmaticProgrammer,PragmaticProgramming,PragmaticBookshelfandthelinkingg
devicearetrademarksofThePragmaticProgrammers,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
theuseofinformation(includingprogramlistings)containedherein.
Our Pragmatic courses, workshops, and other products can help you and your team
create better software and have more fun. For more information, as well as the latest
Pragmatictitles,pleasevisitusathttp://www.pragprog.com.
Copyright©2011PragmaticProgrammers,LLC.
Allrightsreserved.
Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmit-
ted, in any form, or by any means, electronic, mechanical, photocopying, recording, or
otherwise,withoutthepriorconsentofthepublisher.
PrintedintheUnitedStatesofAmerica.
ISBN-10:1-934356-74-3
ISBN-13:978-1-934356-74-6
Printedonacid-freepaper.
B1.0printing,March9,2011
Version:2011-3-10
Prepared exclusively for Mary Smithson
Contents
1 Introduction 7
Part I—Basic UI Recipes 11
1. Add a Basic Splash Screen Transition . . . . . . . . 13
2. Stylize Your Splash Screen Transition . . . . . . . . 18
3. Animate a Custom Notification View . . . . . . . . . 24
4. Create Reusable Toggle Buttons . . . . . . . . . . . 29
5. Form Rounded Views With Textured Colors . . . . . 33
6. Put Together a Reusable Web View . . . . . . . . . . 37
7. Customize Sliders and Progress Views . . . . . . . . 41
8. Shape a Custom Gesture Recognizer . . . . . . . . . 44
9. Create Self-Contained Alert Views . . . . . . . . . . 49
10. Make a Label for Attributed Strings. . . . . . . . . . 55
11. Scroll an Infinite Wall of Album Art . . . . . . . . . . 60
12. Play Tracks from a Wall of Album Art . . . . . . . . 66
13. Have Fun with Auto-Scrolling Text Views . . . . . . 73
Part II—Table and Scroll View Recipes 77
14. Locate Table Cell Subviews . . . . . . . . . . . . . . 79
15. Simplify Table Cell Production . . . . . . . . . . . . 82
16. Use Smart Table Cells in a Nib . . . . . . . . . . . . 86
17. Organize Complex Table Views . . . . . . . . . . . . 91
18. Produce Two-Tone Table Views . . . . . . . . . . . . 97
19. Add Border Shadows for Table Views . . . . . . . . . 98
20. Stationary Content in a Zoomable Scroll View . . . 99
21. Build a Carousel Paging Scroll View . . . . . . . . . 104
Part III—Graphics Recipes 109
Prepared exclusively for Mary Smithson
CONTENTS 6
22 Graphics Recipes 110
22. Draw Gradient Filled Bezier Paths . . . . . . . . . . 112
23. Create Dynamic Images With Multiple Animations . 118
24. Composite and Transform Views . . . . . . . . . . . 121
25. Animate a Gradient Layer . . . . . . . . . . . . . . . 125
26. Reshape Shadows . . . . . . . . . . . . . . . . . . . . 129
27. Display Animated Views . . . . . . . . . . . . . . . . 132
28. Construct a Simple Emitter . . . . . . . . . . . . . . 136
29. Curl the Page to a New View . . . . . . . . . . . . . . 141
Part IV—Networking Recipes 148
30. Tame the Network Activity Indicator . . . . . . . . . 150
31. Simplify Web Service Connections . . . . . . . . . . 153
32. Format a Simple HTTP POST . . . . . . . . . . . . . 157
33. Upload Files Over HTTP . . . . . . . . . . . . . . . . 162
Part V—Runtime and Debugging Recipes 170
34. Leverage Modern Objective-C Class Design . . . . . 172
35. Produce Intelligent Debug Output . . . . . . . . . . 176
36. Design Smarter User Defaults Access . . . . . . . . 180
37. Scan and Traverse View Hierarchies . . . . . . . . . 184
38. Initialize a Basic Data Model. . . . . . . . . . . . . . 185
39. Store Data in a Category . . . . . . . . . . . . . . . . 186
Index 190
Reporterratum
Prepared exclusively for Mary Smithson
thiscopyis(B1.0printing,March9,2011)
Chapter 1
Introduction
Our goal as programmers is to solve problems. Sometimes the prob-
lems are hard, sometimes they’re easy, and sometimes they’re even
fun. Maybe they’re not even “problems” in the colloquial sense of the
word, but we are there to solve them.
Ourgoal asauthors is tohelpyousolveyour problemsbetterandmore
quickly than before—–preferably in that order. A recipe book is unique
in that the authors choose a specific set of tasks and problems and
attack them explicitly, rather than educate at a high, conceptual level.
That’s not to say a recipe book shouldn’t educate. The blessing of a
recipebookcomeswithtrust:youarelookingfortrustworthysolutions
to problems that you don’t feel like discovering on your own. The curse
ofarecipebook,ifyouallowit,isthatyoucopyandpastethesolutions
without taking the time to understand them. It’s always great to save
timebywritinglesscode.Butit’sjustasgreattothinkandlearnabout
how you saved that time, and how you can save more of it moving
forward.
We developed the recipes in this book with these ideas in mind. The
recipesshowyouhowtogetfromstarttofinish,ofcourse,butwehope
they also encourage you to think about when and why to choose a cer-
tainpath:thereareoftenmultipleoptions,especiallyinanenvironment
like Cocoa.
Many of these recipes were also written for maximum reusability. We
weren’t just satisfied demonstrating a technique, or a snippet of code
that got the job done; we wanted to build solutions that were ready
for integration into projects of any kind. Some recipes were born from
existing projects, and others will find their way into new ones with zero
Prepared exclusively for Mary Smithson
CHAPTER 1. INTRODUCTION 8
changes. We’ve learned a lot during the process of writing this book, as
we do during any project. We certainly hope you’ll learn something by
reading it.
Cocoaisarather“opinionated”framework,andsoopinionsonapproach
are both common and passionate in the Mac and iOS communities. In
theinterestofconsistency,wemadesomedecisionsearlyonaboutcer-
tain patterns and approaches to use in this book. The techniques you
see may be familiar to you; they may be employed in a way you hadn’t
considered; or you may simply have never seen them before. Regard-
less, we’d like to explain some of them up front so that there are no
surprises.
Formatting and Syntax
A number of code snippets in this book are specially formatted to fit
thepage.AverboselanguagelikeObjective-Cdoesn’talwaysplaynicely
withcharacterlimits,sosomeofthecodemaysometimeslookunusual.
Youmayencountertersemethodorvariablenames,aseeminglyexces-
sive number of temporary variables, and odd carriage returns. We’ve
tried to preserve the “spirit” of Cocoa convention as much as possible,
butinafewplacestheprintedpagewon.Don’tbealarmedifthecoding
style suddenly changes from time to time.
Categories
A fair number of recipes make use of categories on standard Apple
classes to accomplish tasks. Categories are an incredibly powerful fea-
ture of the Objective-C programming language, and they tend to alien-
ate new Cocoa programmers. They aren’t to be feared, but they are to
berespected.Categoriescanquicklypollutenamespacesandcreate(or
mask)unexpectedbehaviorincomplexclasshierarchies.Whenconsid-
ering a category:
1. Ask yourself if a subclass, or a brand-new class, would be more
appropriate.AsTheObjective-CProgrammingLanguagefromApple
states: “A category is not a substitute for a subclass.”
2. Always prefix category methods when extending a class you don’t
control (for example, UIApplication), to avoid symbol collisions
with future APIs.
Reporterratum
Prepared exclusively for Mary Smithson
thiscopyis(B1.0printing,March9,2011)
CHAPTER 1. INTRODUCTION 9
3. Never override defined methods such as -drawRect: in a category.
Doing so breaks the inheritance tree by masking the source class
implementation.
Synthesized Instance Variables
You’llfindfew,ifany,instancevariable(“ivar”)declarationsintheheader
files and examples that accompany this book. We’ve chosen to exclu-
sively use Objective-C 2.0 properties, with the modern runtime’s ivar
synthesis feature, for declaring class storage. The result is less typing
and less reading, so we can concentrate on the recipe itself.
Private Class Extensions
PrivateclassextensionsareanotherrelativelynewfeatureofObjective-
C,andthey’refrequentlyusedinthisbook.Privateextensionsincrease
readability by minimizing header noise, and they also paint a much
clearer picture for adopters or maintainers of your code. The “Lever-
aging Modern Objective-C Class Design” recipe introduces both private
class extensions and synthesized instance variables for those unfamil-
iar with either technique.
Cleanup in -dealloc
In addition to releasing all relevant instance variables in the -dealloc,
our examples set them to nil. This practice is one of the most hotly
debated topics among Cocoa programmers, and both sides of the argu-
mentholdweight.Thisbookisnotmeanttoparticipateinthedebateat
all: we set them to nil, but that doesn’t mean you have to. If you don’t
like nil-in-dealloc, feel free to leave it out of your own code.
Blocks vs. Delegation
Blocks are a new feature added to C and Objective-C in Mac OS X
Snow Leopard and iOS 4.0. Due to the relative youth of this feature,
the debate on when to use blocks or delegates remains heated. This
book uses both at what we felt were appropriate times. You’re more
than welcome to add blocks to a recipe that uses delegates, or vice
versa. Our goal is ultimately to help you find the simplest and most
natural solutions you can.
Reporterratum
Prepared exclusively for Mary Smithson
thiscopyis(B1.0printing,March9,2011)
CHAPTER 1. INTRODUCTION 10
Aboveall,thisbookisaboutreducingcomplexityandrepetitioninyour
code. We shouldn’t be satisfied with just solving a problem as soon
as possible: we want the solution readily available for the long run.
We hope you agree, and that the ideas in these pages aid you in your
journey as an iOS developer.
Reporterratum
Prepared exclusively for Mary Smithson
thiscopyis(B1.0printing,March9,2011)