2. What is iOS ?
What are the requirement to develop iOS application ?
What is Objective C ?
How to develop Simple iOS Application ?
3. What is iOS ?
iOS which was previously called iPhone OS is a
mobile operating system developed by Apple .
Its first release was in 2007 which included iPhone
and iPod Touch. iPad (1st Generation) was released
in the April 2010 and iPad mini was released in
November 2012 .
iOS is derived from OS X, with which it shares the
Darwin foundation.
4. Requirements
Must have a mac .
Xcode
Xcode is Apple’s integrated development environment (IDE).
Xcode includes a source editor, a graphical user interface
editor, and many other features.
iOS SDK .
5. Objective C
The language used in iOS development is objective C. Its
additions to C language and mostly based on
Smalltalk, one of the first object-oriented
programming languages. Objective-C is a simple language.
Its syntax is small, unambiguous, and easy to learn .
Class
Instance.
Instance Variable
Method
7. Class
In objective C the file where the declaration of class is done is
called the interface file and the file where the class is defined is
called the implementation file.
A simple interface file MyClass.h would look like the following.
@interface MyClass : NSObject{
// class variable declared here
}
// class properties declared here
// class methods and instance methods declared here
@end
8. The implementation file MyClass.m would be like follows
@implementation MyClass
// class methods defined here
@end
9. Instance
Object creation is done as follows
MyClass *objectName = [[MyClass alloc]init] ;
Instance Variable Declaration
@interface MyClass : NSObject{
// Instance variable declared here
}
// class properties declared here
// class methods and instance methods declared here
@end
Instance Variables
10. Methods
Instance Method
Method is declared in objective C as follows
-(returnType) methodName : (typeName) variable1 :
(typeName)variable2;
To call this method in the same class we use the following
statement
[self calculateAreaForRectangleWithLength:30
andBreadth:20];
11. Class method
Class methods can be accessed directly without creating
objects for the class. They don't have any objects associated
with it. An example is shown below.
+(void)simpleClassMethod;
It can be accessed by using the class name
[MyClass simpleClassMethod];
13. An object’s properties let other objects inspect or change
its state. Accessor methods (getters and setters) are used
as an abstraction for interacting with the object’s
underlying data.
@property (getter=isRunning, readonly) BOOL running;
The goal of the @property directive is to make it easy to
create and configure properties by automatically
generating these accessor methods.
14. Protocol
A protocol is a group of related properties and methods
that can be implemented by any class. They are more
flexible than a normal class interface, since they let you
reuse a single API declaration in completely unrelated
classes.
Protocol Declaration
@protocol StreetLegal <NSObject>
- (void)signalStop;
- (void)signalLeftTurn;
- (void)signalRightTurn;
@end
16. Categories
Categories are a way to split a single class definition into
multiple files. Their goal is to ease the burden of
maintaining large code bases by modularizing a class.
Categories work just like normal class definitions in that
they are composed of an interface and an implementation.
17. NSObject is the “root” object in Objective-C
No direct access to instance variables so we write
some get/set “instance methods”
Instance methods (affect internal state of class) are
preceded with a minus sign
“Class methods” (higher level functions) are
preceded with a plus sign e.g. create new class
Points To Remember
18. alloc is equivalent to C++ new but it also zeros all
variables
init should be applied to an instance before use
These are often combined in shorthand:
ComputerScience* ituCompSci = [[ComputerScience alloc]
init];
There is no garbage collection on the iPhone, so we
should release all of our instance memory.
