Objective C Basics For Begineers

The Objective-C programming language is the primary language selected by Apple for writing the applications for Mac, iPode and iPhone. To learn Objective-C you must have prior programming experience in C language. If you have good knowledge of C then you can learn Objective C quickly and start developing applications for iPhone and Mac operating systems.

This tutorial will help the programmers to learn the required skills to develop full-featured applications, utilizing the best features of Objective c like views and controls, menu items etc.


1. Objective C Fundamentals
2. Understanding the Objective C OOPs concepts
3. Memory management in Objective C
4. Objective C Foundation framework
5. Files and I/O operations
6. Advance topics like Introspection, Categories, Forwarding, Dynamic Loading etc.
Objective C Introduction
Objective C is very old programming language and it was designed and developed in 1980. Now Objective C has become popular once again as it is being used by Apple to developing applications for Mac system and iPhone.

Objective-C was designed by Brad Cox in his company Stepstone Corporation in early 1980's. The Objective-C language is designed to enable a easier and powerful object-oriented programming. It works as a powerful set of extensions to the C language. Objective C takes best features from C and smalltalk. Objective C is easy to learn and has full object oriented capabilities.
Objective C is simple and very intuitive programming language that makes the Object Oriented programming sample and sophisticated. Objective C is simple and small but it is a very powerful extension of standard ANSI C language. Objective C provides full object oriented programming capabilities just like C and all these things are done in very simple and straightforward way.
Most of the programming language provides:
• A library of Objects
• Necessary development tools
• OOP' support and related libraries

Like an object oriented language Objective C revolves around objects. It has three parts:
1. inter- face
Interface of a class is generally defined in header file suffixed .h. It is a declaration of a class.

2. implementation
Actual code is written in implementation of a class is generally defined in file of suffixed .m. It is a definition of a class.

3. Instantiation
After declaring and defining class we can be instantiated by allocating memory to the new object of the class.
Features:
It has a lot of features to make a powerful and object oriented program in a easier way. Some are listed below:
1. It is a powerful language,
2. Easy-to-learn,
3. Object-oriented version of C,
4. Provide dynamic binding,
5. Run-time type identification, and persistence
6. Easy to understand code
7. Well organized language

Objective-C’s dynamism has two major benefits:

1. It supports an open dynamic binding that creates a simple architecture to interactive user interface.

2. It enables to development of sophisticated development tools. An interface to the run time system gives a facility to access the information about application at
rum time this makes possible to monitor objective-C application.

Access Modifiers and Garbage Collection:

Previously it was a requirement to allocate and release memory manually to assist with this problem it provides a reference-counting memory management system through retain and release keywords. But it is still required to take care of memory management by the programmer.
garbage collector is implemented as a conservative collector. This enable users to use full functionality of C as well as preserves Objective-C's ability to integrate with C++ code and libraries

Access Privileges

1. Default access in objective-C is @protected.
2. Like C++ objective-C provide public and private access modifiers as well.
3. @protected accessifier enable access elements in the subclass.

Example:

MyClass.h

#import
@interface MyClass:NSObject {
@private
int a;
int b;
}
-(void) set:(int) x andb:(int) y;
-(void) sum;
-(void)show;
@end
MyClass.m 
#import
#import"MyClass.h"
@implementation MyClass
-(void) set:(int) x andb:(int) y {
a=x;
b=y;
}
-(void) sum {
printf("Sum is : %d \n",a+b);
}
-(void)show{
printf("value of a is : %d \n",a);
printf("value of b is : %d \n",b);
}
@end

MyClassMain.m 

#import
#import"MyClass.m"
int main(){
MyClass *class1 = [[MyClass alloc] init];
MyClass *class2 = [[MyClass alloc] init];
[class1 set: 10 andb :12];
[class1 show];
[class1 sum];
// This is invalid statement because variable a is private.
// class2->a = 10;
class2->b = 15;
[class2 show];
[class2 sum];
[class1 release];
[class1 release];
return ;
}

Output: 
value of a is : 10
value of b is : 12
Sum is : 22
value of a is : 0
value of b is : 15
Sum is : 15 


                                              
 
NSObject is the root class of most Objective-C class hierarchies. Through NSObject, objects inherit a basic interface to the runtime system and the ability to behave as Objective-C objects.
Objective C Constructors
Objective-C enables user to define constructor with the help of self and super keywords. Like java Objective-C has parent class and programmer can access its constructor by statement [super init], this statement returns a instance of parent class which we assign to the 'self' keyword, actually 'self' plays same role as this keyword in C++ and Java. The default constructor is -(id) init statement if(self) is used to check the condition self != nil to confirm that parent class returned a new object successfully.
Example:

MyClass.h 

#import
@interface MyClass:NSObject{
int a;
int b;
}
// declare constructor
-(MyClass*) set:(int) a andb:(int) b;
-(void) sum;
@end
MyClass.m
#import
#import"MyClass.h"
@implementation MyClass
// define constructor
-(MyClass*) set:(int) x andb:(int) y {
self = [super init];
if(self) {
a=x;
b=y;
return self;
}
}
-(void) sum {
printf("Sum is : %d",a+b);
}
@end

MyClassMain.m

#import
#import"MyClass.m"
int main(){

// use constructor
MyClass *class = [[MyClass alloc] set : 10 andb : 12];
[class sum];
[class release];
return ;
}

Output:
Sum is : 22