ios basics

Agenda
Basics of iOS
Introduction to iOS
 What is iOS
 Architecture
 Design Patterns
Cocoa Touch Framework
 What is Cocoa Touch Framework
 Complete Assortment of Frameworks
iOS Application Design
 MVC
 Core Application Objects
 Application Life Cycle

Introduction to iOS
What is iOS?
iOS (known as iPhone OS before June 2010) is Apple's
mobile operating system. Originally developed for the iPhone, it has
since been extended to support other Apple, Inc. devices such as the
iPod touch, iPad and Apple TV. Apple, Inc. does not license iOS for
installation on third-party hardware.

Architecture
Core OS:
This level contains the kernel, the file system, networking infrastructure,
security, power management, and a number of device drivers. It also has the
libSystem library, which supports the POSIX/BSD 4.4/C99 API specifications and
includes system-level APIs for many services.

Architecture
Core Services:
The frameworks in this layer provide core services, such as string
manipulation, collection management, networking, URL utilities,
contact management, and preferences. They also provide services
based on hardware features of a device, such as the GPS, compass,
accelerometer, and gyroscope. Examples of frameworks in this layer
are Core Location, Core Motion, and system configuration.

Architecture
Media:
The frameworks and services in this layer depend on the Core Services layer and
provide graphical and multimedia services to the Cocoa Touch layer. They include
Core Graphics, Core Text, OpenGL ES, Core Animation, AVFoundation, Core Audio, and
video playback.

Architecture
Cocoa Touch:
The frameworks in this layer directly support applications based in iOS. They include
frameworks such as Game Kit, Map Kit, and iAd.The Cocoa Touch layer and the Core
Services layer each has an Objective-C framework that is especially important for
developing applications for iOS. These are the core Cocoa frameworks in iOS:

Architecture
UIKit:
This framework provides the objects an application displays in
its user interface and defines the structure for application
behavior, including event handling and drawing.
Foundation:
This framework defines the basic behavior of objects,
establishes mechanisms for their management, and provides
objects for primitive data types, collections, and operating-
system services. Foundation is essentially an object-oriented
version of the Core Foundation framework.

Design Patterns
 Model-View-Controller
 Is a way of dividing your code into independent functional areas. The model
portion defines your application’s underlying data engine and is responsible for
maintaining the integrity of that data. The view portion defines the user
interface for your application and has no explicit knowledge of the origin of
the data displayed in that interface. The controller portion acts as a bridge
between the model and view and coordinates the passing of data between
them.
 Block objects
 Block objects are a convenient way to encapsulate code and local stack
variables in a form that can be executed later. Support for block objects is
available in iOS 4 and later, where blocks often act as callbacks for
asynchronous tasks.
 Delegation
 The delegation design pattern is a way of modifying complex objects without
sub classing them. Instead of sub classing, you use the complex object as is
and put any custom code for modifying the behavior of that object inside a
separate object, which is referred to as the delegate object. At predefined
times, the complex object then calls the methods of the delegate object to
give it a chance to run its custom code.

Design Patterns
 Managed memory model
 The Objective-C language uses a reference-counted scheme for
determining when to release objects from memory. When an object is first
created, it is given a reference count of 1. Other objects can then use the
retain, release, or autorelease methods of the object to increase or
decrease that reference count appropriately. When an object’s reference
count reaches 0, the Objective-C runtime calls the object’s cleanup
routines and then deallocates it.
 Threads and concurrent programming
 All versions of iOS support the creation of operation objects and
secondary threads. In iOS 4 and later, applications can also use Grand
Central Dispatch (GCD) to execute tasks concurrently.

Cocoa Touch Framework
Cocoa touch is Apple's name for the collection of frameworks, APIs, and
accompanying runtimes that make up the development layer of iPhone OS. By
developing with the Cocoa touch frameworks you will be writing applications the
same way that iPhone OS itself is written, with controlled access to the
operating system.
 Much of Cocoa Touch is implemented in Objective-C, an object-oriented
language that is compiled to run at incredible speed, yet employs a truly
dynamic runtime making it uniquely flexible. Because Objective-C is a superset
of C, it is easy to mix C and even C++ into your Cocoa Touch applications.
 As your application runs, the Objective-C runtime instantiates objects based on
executing logic — not just in ways defined during compilation. For example, a
running Objective-C application can load an interface (a nib file created by
Interface Builder), connect the Cocoa objects in the interface to your
application code, then run the correct method once the UI button is pressed. No
recompiling is necessary.

Complete Assortment of Frameworks
In addition to UIKit, the Cocoa Touch collection of frameworks
includes everything needed to create world-class iOS apps,
They are,
 3D graphics
 Professional audio
 Networking
 Camera API
 GPS
 System Level Access API

Core Animation
Use Core Animation to create rich user experiences from an
easy programming model based on compositing
independent layers of graphics
Core Audio
Core Audio is the professional-grade technology for
playing, processing and recording audio, making it easy
to add powerful audio features to your application
Core Data
Core Data provides an object-oriented data
management solution that is easy to use and
understand, yet is built to handle the data model
needs of any application, large or small.

Features List: Frameworks by Category
Below is a small sampling of the available frameworks included in
Cocoa Touch:
Audio and Video
•Core Audio
•OpenAL
•Media Library
•AV Foundation
Graphics and
Animation
•Core Animation
•OpenGL ES
•Quartz 2D
User
Applications
•Address Book
•Core Location
•Map Kit
•Store Kit
Data Management
•Core Data
•SQLite
Networking and Internet
•Bonjour
•WebKit
•BSD Sockets

Features Of Cocoa Application
 Basic application framework
 User-interface objects
 Drawing and imaging
 System interaction
 Performance
 Internationalization
 Text
 Preferences
 Networking
 Printing
 Undo management
 Multimedia
 Data exchange

MVC Architecture
A design pattern in which the model (any data in your program), the
view (what the user sees), and the controller (a layer that handles all
interaction between the view and model) are separated in such a manner that
modifying either the view or model component of your program has no effect
on one another.

MVC Architecture - Model
 A model represents an application’s data and contains the logic for accessing
and manipulating that data.
 Any data that is part of the persistent state of the application should reside in
the model objects.
 The services that a model exposes must be generic enough to support a variety
of clients.
 Model services are accessed by the controller for either querying or effecting a
change in the model state.

MVC Architecture - View
• The view is not dependent on the application logic. It remains same if there is
any modification in the business logic the view is responsible for rendering the
state of the model.
• The presentation semantics are encapsulated within the view, therefore model
data can be adapted for several different kinds of clients.
• The view modifies itself when a change in the model is communicated to the
view. A view forwards user input to the controller.

MVC Architecture - Controller
 Controller accepts and intercepts user requests and controls the business
objects to fulfill these requests.
 An application has one controller for related functionality.
 Controller can also be depends on the type of clients.

Core Application Objects
 From the time our application is launched by the user, to the time it exits, the
UIKit framework manages most of the application’s core behavior. For example,
an iOS application receives events continuously from the system and must
respond to those events. Receiving the events is the job of the UIApplication
object, but responding to the events is the responsibility of your custom code.
 Key Objects in iOS:
 UIApplication object
 Application delegate object
 Data model objects
 View controller objects
 UIWindow Object
 View, Control, and layer objects

Application Life Cycle
The application life cycle constitutes the sequence of events that
occurs between the launch and termination of your application. In iOS, the user
launches your application by tapping its icon on the Home screen. Shortly after
the tap occurs, the system displays some transitional graphics and proceeds to
launch your application by calling its main function. From this point on, the
bulk of the initialization work is handed over to UIKit, which loads the
application’s main bib file and readies the event loop.

Responding To App Termination
Although applications are generally moved to the background and
suspended, if any of the following conditions are true, your application is
terminated and purged from memory instead of being moved to the background:
 The application is linked against a version of iOS earlier than 4.0.
 Application is deployed on a device running a version of iOS earlier than 4.0
 The current device does not support multitasking
 The application includes the UIApplicationExitsOnSuspend key in its Info.plist
file

ios basics

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