COMP 446 / ELEC 446
Mobile Device Applications
Scott Cutler
Professor in the Practice of Computer Technology
Department of Computer Science
Department of Electrical and Computer Engineering
cutler@rice.edu
9/25/12
Wednesday 2-3:30, DH 1046
Agenda
 Events of the Week
 Syllabus
 Review of Assignment 1
 Next week’s assignment and class
 Some more on Objective C
 Questions on Assignment #2
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Event of the Week
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Events of the Week
 HTC has 'no intention' to settle with Apple, say reports
 Apple Requests U.S. Sales Ban on Eight Samsung Devices
 Apple's Victory vs. Samsung Is Patently Meaningless
 Nokia teases September 5 event, says 'things are about to change‘
 Amazon taps Nokia for Kindle Fire maps, report says
 Amazon's Appstore expands to five European countries
 Kindle Fire 'sold out' as new model looms
 Samsung goes all in with Windows 8 in new line of devices
 Windows 8, Windows Phone 8 launch dates revealed
 Windows Phone 8 Gets a Chance to Shine
 Windows Server 2012 launches as cornerstone of Microsoft's 'Cloud OS'
 HP, Dell, Lenovo, Others Pack Tablet Market at IFA 2012
 Google, Apple CEOs Talk While Their Patent Battles Rage: Report
 Google Street View Brings 'Punch Buggy' Game Online
 'Eastwooding' meme sweeps across Twitter
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Current Roster
 Victor Acuna
 Ryan Artecona
 Gbenga Badipe
 Joel Baranowski
 Peter Chang
 Joan Chao
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Current Roster (2)
 Alex Chiu
 Heaven Chen
 Lingo Dai
 Weibo He
 Sahil Hingorani
 Zhehao Li
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Current Roster (3)
 Abdul Nimeri
 Bill Robertson
 Frank Salinas
 Tyler Siegert
 Austin Witt
 Matthew Zhao
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Optional Sessions and Support
 Monday office hours with TA Richard Latimer. 4:00pm Mudd
 Additional session Thursday, 9pm on 8/30 and 9/6.
 Ability to email questions to me at any time.
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Can email Richard Latimer as well.
 Level of support will vary over semester
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High level of support at the beginning.
Support decreasing each project as over time as knowing
where to look or how to debug is a very important skill for
you to learn.
Richard instructed to respond conceptually – not just provide
solutions.
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COMP 446 (tentative) Syllabus
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Lecture 1 - 8/22/12 - Introduction
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1, 2
#2 – Function Calculator
Friday, 9/7 6:00 am (Thursday 30:00)
Watch before:
Assignment:
Assignment due:
3, 4 (demo part)
#3 – Graphing Universal Calculator
Tuesday, 9/18 6:00 am (Monday 30:00)
Lecture 4 - 9/12/12 - Assignment 3 issues and questions from videos
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Watch before:
Assignment:
Assignment due:
Lecture 3 - 9/05/12 - Assignment 2 issues and questions from videos
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None
#1 - Calculator
Friday, 8/31 6:00 am (Thursday 30:00)
Lecture 2 - 8/29/12- Assignment 1 issues and questions from videos
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Watch before:
Assignment:
Assignment due:
Watch before:
Assignment:
Assignment due:
4 (post demo), 5, 6
Continue with #3 – Graphing Universal Calculator
Tuesday, 9/18 6:00 am (Monday 30:00)
Lecture 5 - 9/19/12 - Assignment 3 issues and questions from videos
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Watch before:
Assignment:
Assignment due:
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Watch 7 before class, 8 after class
#4 – Fiickr Top Places
Friday, 9/28 6:00 am (Thursday 30:00)
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COMP 446 (tentative) Syllabus
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Lecture 6 - 9/26/12 - Assignment 4 issues and questions from videos
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Watch before:
Assignment:
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Assignment due:
10 (after Tab Bar), 11, 12
1: #6 – Fiickr Core Data
- Likely to be broken into required and optional parts
- Optional part required for A+
2: Final Project Topic (due before next class)
Friday, 10/12 6:00 am (Thursday 30:00)
Lecture 8 - 10/10/12 - Assignment 6 issues and SQL
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8, 9 very beginning of 10
#5 – Fiickr Map Places
Friday, 10/5 6:00 am (Thursday 30:00)
Lecture 7 - 10/03/12 - Assignment 5 issues and questions from videos
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Watch before:
Assignment:
Assignment due:
Watch before:
Assignment:
Assignment due:
13, 14
Final Project Proposal
Tuesday, 10/16 6:00 am (Monday 30:00)
Lecture 9 - 10/17/12 - iOS 6
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Watch before:
Assignment:
Assignment due:
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Optional 15, 16
iOS 6 app
Friday, 10/26 6:00 am (Thursday 30:00)
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COMP 446 (tentative) Syllabus
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Lecture 10 - 10/24/12 – HTML 5
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Assignment:
Assignment due:
Continue working on Final Project
Wednesday, 11/28 2:00pm
Assignment:
Assignment due:
Continue working on Final Project
Wednesday, 11/28 2:00pm
Lecture 14 - 11/21/12 – No class, but continue on final project
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Continue working on Final Project
Wednesday, 11/28 2:00pm
Lecture 13 - 11/14/12 - Individual meetings on Final Project
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Assignment:
Assignment due:
Lecture 12 - 11/7/12- Android vs. iOS vs. Windows Phone group debate
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Optional 17, 18
Major Final Project Feature
Friday, 11/2 6:00 am (Thursday 30:00)
Lecture 11 - 10/31/12 - TBD
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Watch before:
Assignment:
Assignment due:
Assignment:
Assignment due:
Continue working on Final Project
Wednesday, 11/28 2:00pm
Lecture 15 - 11/28/12 - Final Presentations
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Assignment:
Assignment due:
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Document Final Project
By time assigned for COMP 446 final (there is NO final exam)
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Week 4
 Watch CS193p lectures #4 (after demo), #5, #6 before class
 Make progress on CS193p Assignment #3
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Try and complete before next class. Due Tuesday, 9/18 6:00 am .
 Submit assignments, review lectures at www.comp446.com
 Start thinking about big project
 Next week’s lecture – Objective C Core Graphics
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Assignment #1 Comments
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Review of Video 3 Items
 Many of the slides to follow come directly
from the Fall 2011 Stanford CS193p slide
deck.
 Some come from earlier versions of CS193p
which I think were a bit clearer than the
current deck
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All Those Symbols
;
@
+
 //
-
.
{}
#
[]
!
()
 +=
*
%
 **
 ==
:
^
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strong vs weak
 strong “keep this in the heap until I don’t point to it anymore”
 I won’t point to it anymore if I set my pointer to it to nil.
 Or if I myself am removed from the heap because no one strongly points to me!
 weak “keep this as long as someone else points to it strongly”
 If it gets thrown out of the heap, set my pointer to it to nil automatically (if user on
iOS 5 only).
 This is not garbage collection!
 It’s way better. It’s reference counting done automatically for you.
 Finding out that you are about to leave the heap
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A special method, dealloc, is called on you when your instance’s memory is freed from the
heap.
You will rarely ever have to implement this method. It’s “too late” to do much useful here.
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
[super dealloc];
}
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nil
 The value of an object pointer that does not point to anything
id obj = nil;
NSString *hello = nil;
 Like “zero” for a primitive type (int, double, etc.)
 Actually, it’s not “like” zero: it is zero.
 All instance variables start out set to zero
 Thus, instance variables that are pointers to objects start out with the value of nil.
 Can be implicitly tested in an if statement
if (obj) { } // curly braces will execute if obj points to an object
 Sending messages to nil is (mostly) okay. No code gets executed.
 If the method returns a value, it will return zero.
int i = [obj methodWhichReturnsAnInt]; // i will be zero if obj is nil

Be careful if the method returns a C struct. Return value is undefined.
CGPoint p = [obj getLocation]; // p will have an undefined value if obj is nil
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BOOL
 Objective-C’s boolean “type” (actually just a typedef)
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Can be tested implicitly
if (flag) { }
if (!flag) { }
YES means “true,” NO means “false”
NO == 0, YES is anything else
if (flag == YES) { }
if (flag == NO) { }
if (flag != NO) { }
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Instance vs. Class Methods
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Starts with a dash
- (BOOL)dropBomb:(Bomb *)bomb
at: (CGPoint)position
from:(double)altitude;
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“Normal” Instance Methods
Calling syntax
[<pointer to instance> method]
Ship *ship = ...; // instance of a Ship
destroyed = [ship dropBomb:firecracker
at:dropPoint
from:300.0];
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self / super is calling instance
self means “my implementation”
super means “my superclass’s
implementation”
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Starts with a plus sign
+ (id) alloc;
+ (Ship *)motherShip;
+ (NSString *)stringWithFormat:...
Creation & Utility Methods
Calling syntax
[Class method]
Ship *ship = [Ship motherShip];
NSString *resultString =
[NSString stringWithFormat:@“%g”, result];
[[ship class] doSomething];
self / super is this class
self means “this class’s class methods”
super means “this class’s superclass’s class
methods”
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Instantiation
 Asking other objects to create objects for you
NSString’s - (NSString *)stringByAppendingString:(NSString *)otherString;
NSString’s & NSArray’s - (id)mutableCopy;
NSArray’s - (NSString *)componentsJoinedByString:(NSString *)separator;
 Not all objects handed out by other objects are newly created
NSArray’s - (id)lastObject;
NSArray’s - (id)objectAtIndex:(int)index;
Unless the method has the word “copy” in it, if the object already exists, you get a pointer to it.
If the object does not already exist (like the 3 examples above), then you’re creating.
 Using class methods to create objects
NSString’s + (id)stringWithFormat:(NSString *)format, ...
UIButton’s + (id)buttonWithType:(UIButtonType)buttonType;
NSMutableArray’s + (id)arrayWithCapacity:(int)count;
NSArray’s + (id)arrayWithObject:(id)anObject;
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Object Typing
@interface Vehicle
- (void)move;
@end
@interface Ship : Vehicle
- (void)shoot;
@end
Ship *s = [[Ship alloc] init];
[s shoot];
[s move];
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Vehicle *v = s;
[v shoot];
id obj = ...;
[obj shoot];
[obj someMethodNameThatNoObjectAnywhereRespondsTo];
NSString *hello = @”hello”;
[hello shoot];
Ship *helloShip = (Ship *)hello;
[helloShip shoot];
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Introspection
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All objects that inherit from NSObject know these methods
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isKindOfClass: returns whether an object is that kind of class (inheritance included)
isMemberOfClass: returns whether an object is that kind of class (no inheritance)
respondsToSelector: returns whether an object responds to a given method
Method testing methods take a selector (SEL)
Special @selector() directive turns the name of a method into a selector
if ([obj respondsToSelector:@selector(shoot)]) {
[obj shoot];
} else if ([obj respondsToSelector:@selector(shootAt:)]) {
[obj shootAt:target];
}
SEL is the Objective-C “type” for a selector
SEL shootSelector = @selector(shoot);
SEL shootAtSelector = @selector(shootAt:);
SEL moveToSelector = @selector(moveTo:withPenColor:);
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Frameworks
 A collection of pre-written and debugged code
 Foundation contains base class for much in iOS SDK
 MANY other frameworks available; some of which you will
use for later assignments and your final project.
 Frameworks help make difficult things amazingly easy
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Foundation Framework
 Value and collection classes
 User defaults
 Archiving
 Notifications
 Undo manager
 Tasks, timers, threads
 File system, pipes, I/O, bundles
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NSObject
 Root class
 Implements many basics
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Memory management
Introspection
Object equality
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NSString
 General-purpose Unicode string support
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Unicode is a coding system which represents all of the
world’s languages
 Consistently used throughout Cocoa Touch instead of “char *”
 Without doubt the most commonly used class
 Easy to support any language in the world with Cocoa
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String Constants
 In C constant strings are
“simple”
 In ObjC, constant strings are
@“just as simple”
 Constant strings are NSString instances
NSString *aString = @”Hello World!”;
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Format Strings
 Similar to printf, but with %@ added for objects
NSString *aString = @”Johnny”;
NSString *log = [NSString stringWithFormat: @”It’s ‘%@’”, aString];
log would be set to It’s ‘Johnny’
 Also used for logging
NSLog(@”I am a %@, I have %d items”, [array className], [array count]);
would log something like:
I am a NSArray, I have 5 items
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NSString
 Often ask an existing string for a new string with modifications
- (NSString *)stringByAppendingString:(NSString *)string;
- (NSString *)stringByAppendingFormat:(NSString *)string;
- (NSString *)stringByDeletingPathComponent;
 Example:
NSString *myString = @”Hello”;
NSString *fullString;
fullString = [myString stringByAppendingString:@” world!”];
fullString would be set to Hello world!
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NSString
 Common NSString methods
- (BOOL)isEqualToString:(NSString *)string;
- (BOOL)hasPrefix:(NSString *)string;
- (int)intValue;
- (double)doubleValue;
 Example:
NSString *myString = @”Hello”;
NSString *otherString = @”449”;
if ([myString hasPrefix:@”He”]) {
// will make it here
}
if ([otherString intValue] > 500) {
// won’t make it here
}
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NSMutableString
 NSMutableString subclasses NSString
 Allows a string to be modified
 Common NSMutableString methods
+ (id)string;
- (void)appendString:(NSString *)string;
- (void)appendFormat:(NSString *)format, ...;
NSMutableString *newString = [NSMutableString string];
[newString appendString:@”Hi”];
[newString appendFormat:@”, my favorite number is: %d”,
[self favoriteNumber]];
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Collections
 Array - ordered collection of objects
 Dictionary - collection of key-value pairs
 Set - unordered collection of unique objects
 Ordered Set - ordered collection of unique objects
 Common enumeration mechanism
 Immutable and mutable versions
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Immutable collections can be shared without side
effect
Prevents unexpected changes
Mutable objects typically carry a performance
overhead
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NSArray
 Common NSArray methods
+ arrayWithObjects:(id)firstObj, ...; // nil terminated!!!
- (unsigned)count;
- (id)objectAtIndex:(unsigned)index;
- (unsigned)indexOfObject:(id)object;
 NSNotFound returned for index if not found
NSArray *array = [NSArray arrayWithObjects:@”Red”, @”Blue”,
@”Green”, nil];
if ([array indexOfObject:@”Purple”] == NSNotFound) {
NSLog (@”No color purple”);
}
 Be careful of the nil termination!!!
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NSMutableArray
 NSMutableArray subclasses NSArray
 So, everything in NSArray
 Common NSMutableArray Methods
+ (NSMutableArray *)array;
- (void)addObject:(id)object;
- (void)removeObject:(id)object;
- (void)removeAllObjects;
- (void)insertObject:(id)object atIndex:(unsigned)index;
NSMutableArray *array = [NSMutableArray array];
[array addObject:@”Red”];
[array addObject:@”Green”];
[array addObject:@”Blue”];
[array removeObjectAtIndex:1];
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NSDictionary
 Common NSDictionary methods
+ dictionaryWithObjectsAndKeys: (id)firstObject, ...;
- (unsigned)count;
- (id)objectForKey:(id)key;
 nil returned if no object found for given key
NSDictionary *colors = [NSDictionary
dictionaryWithObjectsAndKeys:@”Red”, @”Color 1”,
@”Green”, @”Color 2”, @”Blue”, @”Color 3”, nil];
NSString *firstColor = [colors objectForKey:@”Color 1”];
if ([colors objectForKey:@”Color 8”]) {
// won’t make it here
}
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NSMutableDictionary
 NSMutableDictionary subclasses NSDictionary
 Common NSMutableDictionary methods
+ (NSMutableDictionary *)dictionary;
- (void)setObject:(id)object forKey:(id)key;
- (void)removeObjectForKey:(id)key;
- (void)removeAllObjects;
NSMutableDictionary *colors = [NSMutableDictionary dictionary];
[colors setObject:@”Orange” forKey:@”HighlightColor”];
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NSSet
 Unordered collection of objects
 Common NSSet methods
+ setWithObjects:(id)firstObj, ...; // nil terminated
- (unsigned)count;
- (BOOL)containsObject:(id)object;
 NSOrderedSet
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Faster searching
Does not inherit from NSSet
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NSMutableSet
 NSMutableSet subclasses NSSet
 Common NSMutableSet methods
+ (NSMutableSet *)set;
- (void)addObject:(id)object;
- (void)removeObject:(id)object;
- (void)removeAllObjects;
- (void)intersectSet:(NSSet *)otherSet;
- (void)minusSet:(NSSet *)otherSet;
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Enumeration
 Consistent way of enumerating over objects in collections
 Use with NSArray, NSDictionary, NSSet, etc.
NSArray *array = ... ; // assume an array of People objects
// old school
Person *person;
int count = [array count];
for (i = 0; i < count; i++) {
person = [array objectAtIndex:i];
NSLog([person description]);
}
// new school
for (Person *person in array) {
NSLog([person description]);
}
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NSNumber
 In Objective-C, you typically use standard C number types
 NSNumber is used to wrap C number types as objects
 Subclass of NSValue
 No mutable equivalent!
 Common NSNumber methods
+ (NSNumber *)numberWithInt:(int)value;
+ (NSNumber *)numberWithDouble:(double)value;
- (int)intValue;
- (double)doubleValue;
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Other Classes
 NSData / NSMutableData
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Arbitrary sets of bytes
 NSDate / NSCalendarDate
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Times and dates
 NSValue
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Object store for object pointers and other
values like C structures, int, float, char, etc.
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Property List

The term “Property List” just means a collection of collections
Specifically, it is any graph of objects containing only the following classes:
NSArray, NSDictionary, NSNumber, NSString, NSDate, NSData
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An NSArray is a Property List if all its members are too
So an NSArray of NSString is a Property List.
So is an NSArray of NSArray as long as those NSArray’s members are Property Lists.
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An NSDictionary is one only if all keys and values are too
An NSArray of NSDictionarys whose keys are NSStrings and values are NSNumbers
is one.
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Why define this term?
Because the SDK has a number of methods which operate on Property Lists.
Usually to read them from somewhere or write them out to somewhere.
[plist writeToFile:(NSString *)path atomically:(BOOL)]; // plist is NSArray or NSDictionary
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NSUserDefaults
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Lightweight storage of Property Lists.
It’s basically an NSDictionary that persists between launches of your application.
Not a full-on database, so only store small things like user preferences.
Read and write via a shared instance obtained via class method standardUserDefaults
[[NSUserDefaults standardUserDefaults] setArray:rvArray forKey:@“RecentlyViewed”];
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Sample methods:
- (void)setDouble:(double)aDouble forKey:(NSString *)key;
- (NSInteger)integerForKey:(NSString *)key; // NSInteger is a typedef to 32 or 64 bit int
- (void)setObject:(id)obj forKey:(NSString *)key; // obj must be a Property List
- (NSArray *)arrayForKey:(NSString *)key; // will return nil if value for key is not NSArray
Always remember to write the defaults out after each batch of changes!
[[NSUserDefaults standardUserDefaults] synchronize];
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Assignment #2 Questions
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