Iphone course 1

iPhone Application Development 1
Janet Huang
2011/11/23

ALL Schedule

11/23 - iPhone SDK
- Objective-C Basic
- Your First iPhone Application

11/30 - MVC design & UI
- GPS/MAP Application
(CoreLocation & MapKit)
- Google Map API
- LBS Application

12/07 - Network service
- Facebook API
- LBS + Facebook Application

How to study?

- Stanford CS193p
- videos in iTunes U
- all resources on website

- Apple ofﬁcial document

- Good book
- iOS Programming The Big Nerd Ranch Guide

Today’s Topics

• iPhone SDK
• Objective-C
• Common Foundation Class
• Your First iPhone Application

iPhone SDK

• Xcode Tools
• Xcode
• Instruments
• iOS Simulator
• iOS Developer Library

OOP Vocabulary
• Class: define the grouping of data and
code, the “type” of an object
• Instance: a specific allocation of a class
• Method: a “function” that an object knows
how to perform
• Instance variable: a specific piece of data
belonging to an object

OOP Vocabulary
• Encapsulation
• keep implementation private and separate from
interface

• Polymorphism
• different object, same interface

• Inheritance
• hierarchical organization, share code, customize
or extend behaviors

Inheritance

- Hierarchical relation between classes
- Subclass “inherit” behavior and data from superclass
- Subclasses can use, augment or replace superclass methods

Objective-C

• Classes & Objects
• Messaging
• Properties
• Protocols

Classes and Instances
• In obj-c, classes and instances are both
objects
• class is the blueprint to create instances

Classes and Objects
• Classes declare state and behavior
• State (data) is maintained using instance
variables
• Behavior is implemented using methods
• instance variables typically hidden
• accessible only using getter/setter methods

Define a Class
public header private implementation
#import <Foundation/Foundation.h> #import "Person.h"
@interface Person : NSObject { @implementation Person
// instance variables - (int)age {
NSString *name; return age;
int age; }
} - (void)setAge:(int)value {
// method declarations age = value; }
- (NSString *)name; //... and other methods
- (void)setName:(NSString *)value; @end
- (int)age;
- (void)setAge:(int)age;
- (BOOL)canLegallyVote;
- (void)castBallot;
@end
in .h file in .m file

Object Creation
• Two steps
• allocate memory to store the object

• initialize object state

+alloc
class method that knows how much memory is needed

-init
instance method to set initial values, perform other setup

Implementing your own -init method
Person *person = nil;
person = [[Person alloc] init]

#import “Person.h”

@implementation Person

- (id)init {
if(self = [super init]){
age = 0;
name = @”Janet”;
// do other initialization
}
}
Create = Allocate + Initialize

Messaging

• Class method and instance method
• Messaging syntax

Terminology
• Message expression
[receiver method: argument]

• Message

• Selector

• Method
The code selected by a message

Class and Instance
Methods
• instances respond to instance methods
- (id) init;
- (ﬂoat) height;
- (void) walk;
• classes respond to class methods
+ (id) alloc;
+ (id) person;
+ (Person *) sharedPerson;

Messaging
• message syntax
[receiver message]

[receiver message:argument]

[receiver message:arg1 andArg:arg2]

• message declaration
- (void)insertObject:(id)anObject atIndex:(NSUInteger)index;

• call a method or messaging
[myArray insertObject:anObject atIndex:0]

Instance Variables
• Scope default @protected only the class and subclass can access
@private only the class can access
@public anyone can access

• Scope syntax
@interface MyObject : NSObject {
int foo;
@private
int eye;
@protected Protected: foo & bar
int bar;
Private: eye & jet
@public
int forum; Public: forum & apology
int apology;
@private
int jet;
}

• Forget everything on the previous slide!
Mark all of your instance variables @private.
Use @property and “dot notation” to access instance variables.

Accessor methods
• Create getter/setter methods to access instance
variable’s value
@private
int eye;
} * Note the capitalization
- (int)eye; - instance variables always start with lower case
- (void)setEye:(int)anInt; - the letter after “set” MUST be capitalized
@end

• Now anyone can access your instance variable using
“dot syntax”
someObject.eye = newEyeValue; // set the instance variable
int eyeValue = someObject.eye; // get the instance variable’s current value

Properties
@property
Let compiler to help you generate setter/getter method
declarations

@interface MyObject : NSObject { @interface MyObject : NSObject {
@private @private
int eye; int eye;
} }
@property int eye; @property int eye;
- (int)eye;
- (void)setEye:(int)anInt; @end
@end

Properties
• An @property doesn’t have to match an
instance variable

@interface MyObject : NSObject { @interface MyObject : NSObject {
@private }
int p_eye; @property int eye;
} @end
@property int eye;
@end

*They are all perfectly legal!

Properties
• Don’t forget to implement it after you
declare

@implementation MyObject
- (int)eye {
@private
return eye;
int eye;
}
}
- (void)setEye:(int)anInt {
@property int eye;
eye = anInt;
@end
}
@end

Properties
@synthesize
Let compiler to help you with implementation

@interface MyObject : NSObject { @implementation MyObject
@private @synthesize eye;
int eye; - (int)eye {
} return eye;
@property int eye; }
@end - (void)setEye:(int)anInt {
eye = anInt;
}
@end

Properties
• Be careful!!
What’s wrong?
- (void)setEye:(int)anInt
{
self.eye = anInt;
} Inﬁnite loop!!! :(

Can happen with the getter too ...

- (int)eye { if (self.eye > 0) { return eye; } else { return -1; } }

Protocols
@interface MyClass : NSObject <UIApplicationDelegate,
AnotherProtocol> {
}
@end

@protocol MyProtocol
- (void)myProtocolMethod;
@end

Dynamic and static
typing
• Dynamically-typed object
id anObject not id *

• Statically-typed object
Person * anObject

The null pointer: nil
• explicitly if (person == nil) return;

• implicitly if (!person) return;

• assignment person = nil;

• argument [button setTarget: nil];

• send a message to nil
person = nil;
[person castBallot];

BOOL typedef
• Obj-C uses a typedef to define BOOL as a
type
• use YES or NO
BOOL flag = NO;
if (flag == YES)
if (flag)
if (!flag)
if (flag != YES)
flag = YES;
flag = 1;

Foundation Framework
• NSObject
• Strings
• NSString

• NSMutableString

• Collections
• Array

• Dictionary

• Set

NSObject
• Root class
• Implements many basics
• memory management

• introspection

• object equality

- (NSString *)description is a useful method to override (it’s %@ in NSLog()).

String Constants
• C constant strings
“c simple strings”

• Obj-C constant strings
@“obj-c simple strings”

• Constant strings are NSString instances
NSString *aString = @“Hello World!”;

Format Strings
• use %@ to add objects (similar to printf)
NSString *aString = @”World!”;
NSString *result = [NSString stringWithFormat: @”Hello %@”,
aString];

result: Hello World!

• used for logging
NSLog(@”I am a %@, I have %d items.”, [array className], [array count]);

Log output: I am NSArray, I have 5 items.

NSString
• Create an Obj-C string from a C string
NSString *fromCString = [NSString stringWithCString:"A C string"
encoding:NSASCIIStringEncoding];

• Modify an existing string to be a new string
- (NSString *)stringByAppendingString:(NSString *)string;
- (NSString *)stringByAppendingFormat:(NSString *)string;
- (NSString *)stringByDeletingPathComponent;

for example:
NSString *myString = @”Hello”;
NSString *fullString;
fullString = [myString stringByAppendingString:@” world!”];

NSMutableString
• Mutable version of NSString
• Allows a string to be modiﬁed
• Common methods
+ (id)string;
- (void)appendString:(NSString *)string;
- (void)appendFormat:(NSString *)format, ...;

for example:
NSMutableString *newString = [NSMutableString string];
[newString appendString:@”Hi”];
[newString appendFormat:@”, my favorite number is: %d”,
[self favoriteNumber]];

MVC
should
did
will target

controller
outlet
count
Notiﬁcation

de
data

da
& KVO

le
ta

ga
action

te
so
urc
es
model view

General process for building
iPhone application
1.
Create
a
simple
MVC
iPhone
applica5on
2.
Build
interfaces
using
Interface
builder
3.
Declara5ons
a.
Declaring
instance
variables
b.
Declaring
methods
4.
Make
connec5ons
a.
SeDng
a
pointer
b.
SeDng
targets
and
ac5ons
5.
Implemen5ng
methods
a.
Ini5al
method
b.
Ac5on
methods
6.
Build
and
run
on
the
simulator
7.
Test
applica5on
on
the
device

Iphone course 1

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Iphone course 1