How to develop an iOS application

How to develop an iOS application
Objective-C – Xcode – iOS

Le Thanh Quang Mobile tea
April 19th 2012

Agenda

Objective-C in brief

Xcode

iOS frameworks

www.exoplatform.com - Copyright 2012 eXo Platform 2

Objective-C


Objective-C – What is it?

Simple extension of the C language

Adds object-oriented capabilities to C language
Runtime system (C library)
Dynamic typing
Dynamic binding

GCC/Clang compiler supports both C and Objective-C
Apple donated Objective-C for GNU project (open source)


Objective-C – Who use?

Apple Inc.

Mac OS X developers
Cocoa framework
Core animation, Core data, etc
iOS developers
Cocoa touch framework
Core animation, Core data, etc


Objective-C – Why should I (Java developer)
care?
Make up your mind with new code designs

iPhone/iPad devices become popular rich user agents in
enterprise market

eXo Platform 3.5, cloud-workspaces.com are integrated
with iOS based devices and Android family

Play around for fun or profit in free time ;)


Objective-C – History

Appeared in 1983

Designed by Tom Love & Brad Fox

Major implementations GCC, Clang

Inf uenced by
l Smalltalk, C

OS Cross-platform


Objective-C and Java

Java
Almost everywhere
… except iPhone

Objective-C
Platform
Mac OS X
iPhone, iPad, ...


Objective-C and Java Message Syntax

Java

myString.toString()

Objective-C
* Square brackets for message expressions

[myString description]


Objective-C and Java Method arguments

Java

person.setFirstName(“Fred”)

Objective-C
* Arguments are delimited by colons

[person setFirstName:@”Fred”]


Objective-C and Java Object Data types

Java
Employee emp = new Employee();

Objective-C

* Objective-C objects are dynamically allocated structs
Employee *emp = [[Employee alloc] init];

* Providing generic object type, id
id emp2 = [[Employee alloc] init];


Objective-C and Java Object Data types

Java
* Constructors
Employee emp = new Employee();

Objective-C

Employee *emp = [[Employee alloc] init];

* Creation methods are just methods
* Calls to super can occur anywhere within a method
* Inheritance is straight-forward
* Memory allocations and initialization are separate steps


Objective-C and Java Prefix vs Package path

Java
java.lang.String s = new String(“hello”);

Objective-C

* Objective-C doesn't provide namespaces
* Frameworks and libraries use prefixes by convention to avoid collision

NSString *s = [NSString alloc] initWithString:@”Hi”];

==> NS is prefix for classes of Foundation Framework.


Objective-C and Java Method prototypes

Java public void sayHello() {
…
}

Objective-C

* Methods declared in .h file, implemented in .m
* Instance methods prefixed with -
* Class methods prefixed with +
Ex:
// Method declarations
- (id)init;
- (id)alloc;


Objective-C and Java Method prototypes

Objective-C

* No method overloading
* Runtime system looks up methods by name rather than signatures

* Method names can be composed of multiple sections

Ex:
- (void)addEmployee:(Employee *)emp withTitle:
(NSString *)title

Name of method is addEmployee:withTitle


Objective-C and Java Class

Java
...

Objective-C


Objective-C and Java Anatomy of Class Declaration


Objective-C Class Implementation


Objective-C and Java Class

Java
...

Objective-C


Objective-C – Memory management

* Reference counting
(id)retain; // increase retain count
(id)release; // decrease retain count
(id)autorelease; // release with a delay
(void)dealloc; // call by release when retain count = 1
* Creation methods set retain count to 1
Creation methods whose names start with alloc or new or contain copy
Those who call creation methods MUST call either release or
autorelease also
Never call dealloc directly


Objective-C – Memory management


Objective-C – Categories


Objective-C – Using category


Objective-C – Blocks

A block of code
A sequence of statements inside {}
Start with the magical character caret ^

Ex:
[aDictionary enumerateKeysAndObjectsUsingBlock:^(id key,
id value, BOOL *stop) {
NSLog(@“value for key %@ is %@”, key, value);
if ([@“ENOUGH” isEqualToString:key]) {
*stop = YES;
}
}];


A block of code
Can use local variables declared before the block inside the block
But they are read only!

Ex:
double stopValue = 53.5;
[aDictionary enumerateKeysAndObjectsUsingBlock:^(id key,
id value, BOOL *stop) {
NSLog(@“value for key %@ is %@”, key, value);
if ([@“ENOUGH” isEqualToString:key] || ([value
doubleValue] == stopValue)) {
*stop = YES;
stoppedEarly = YES; // ILLEGAL
}
}]; www.exoplatform.com - Copyright 2012 eXo Platform 25

When do we use blocks in iOS?
Enumeration
View Animations
Sorting (sort this thing using a block as the comparison method)
Notification (when something happens, execute this block)
Error handlers (if an error happens while doing this, execute this block)
Completion handlers (when you are done doing this, execute this block)

And a super-important use: Multithreading


Xcode


Xcode
IDE for iPhone projects
Build
Run (Simulator, device)
Debug
Source code management (SCM)
Documentation


Xcode
Automatically maintain build scripts

Display logical grouping of files
No package paths
By default, groups not mapped to folder structure
Resources
Automatically bundled with executable
Frameworks
Linked at compile time; no classpath needed


Xcode - Interface Builder

Visual GUI design tool

Doesn't generate code

Working with “freeze-dried” objects
Archived (serialized) in .nib files
Dynamically loaded
Objects deserialized at load time


Xcode

DEMO


iOS


iOS – Layered architecture

C libraries and system calls

Core services (C libraries and Objective-C
frameworks)

Media Layer (C libraries and Objective-C
frameworks)

Cocoa touch
Foundation framework
UIKit

iOS – Design Patterns

MVC Pattern

Delegate Pattern

Target/Action Pattern


iOS – MVC Pattern

Model View

Controller


iOS – MVC Pattern

Model
Manages the app data and state
No concerned with UI or presentation
Often persists somewhere
Same model should be reusable, unchanged in different interfaces.


iOS – MVC Pattern

View
Present the Model to the user in an appropriate interface
Allows user to manipulate data
Does not store any data
Easily reusable & configurable to display different data


iOS – MVC Pattern

Controller
Intermediary between Model & View
Updates the view when the model changes
Updates the model when the user manipulates the view
Typically where the app logic lives.


iOS – Delegation Pattern
Control passed to delegate objects to perform application
specific behavior

Avoids need to subclass complex objects

Many UIKit classes use delegates
UIApplication
UITableView
UITextField


iOS – Target/Action Pattern

When event occurs, action is invoked on target
object

Target: myObject
sayHello Action: @selector(sayHello)
Event: UIControlEventTouchUpInside

Controller


References

Training for newcomer of Mobile team -
http://int.exoplatform.org/portal/g/:spaces:mobile/mobile/local._wiki.WikiPortl
et/group/spaces/mobile/iOS_Training

Jonathan Lehr -
http://jonathanlehr.files.wordpress.com/2009/09/objective-c-and-java.pdf

stanford.edu - http://www.stanford.edu/class/cs193p/cgi-bin/drupal/


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