Objective-C basic

Objective C

This is a primitive language used in Apple device application development (IOS/Macintosh). The base of this language is c. Objective –C is an easy to understand and object oriented programming language.  Objective – c comes with library, development tool and OOPs.

The basic 3 parts are-

1. inter- face
  Signature class. [*.h file]
2. implementation
Definition of a class.[*.m file]
3. Instantiation
instantiation of class by allocating memory.

It is a dynamic language. It supports open dynamic binding to create easy architecture for user interface.

Basic structure of a program-

#include <stdio.h>

//----Header file added------

int main(void)

{

        printf("Hello!");

        return ;

}

//----------Body Ends-----

Code file extension will be “.m”. It complies line by line. So if we need to call a function in other function, caller function should be bellow of called function.

#include <stdio.h>

-(void) called

{

}

-(void) caller

{

        called();

}

int main(void)

{

        caller();

        return ;

}

For MAC ,Object compilation –

$ gcc -o hello hello.m \ -L /System/Library/Frameworks/Foundation.framework/Foundation

Run compiled code on MAC

$ ./hello

Compiler for Objective – c can be downloaded from - http://www.gnustep.org/experience/Windows.html. [For windows]

 Key Words----

@interface	used to declare of class or interface.
@implementation	used to define a class or category.
@protocol	used to declare a formal protocol.
@end	ends the declaration, definition, category or protocol.
@private	Limits the scope of an instance variable to the class that declares it.
@protected	Limits instance variable scope to declaring and inheriting classes.
@public	Removes restrictions on the scope of instance variables.
@try	Defines a block within which exceptions can be thrown.
@throw	Throws an exception object.
@catch	Catches an exception thrown within the preceding @try block.
@finally	A block of code that is executed whether exceptions were thrown or not in a @try block.
@class	Declares the names of classes defined elsewhere.
@selector(method_name)	It returns the compiled selector that identifies method_name.
@protocol(protocol_name)	Returns the protocol_name protocol (an instance of the Protocol class). (@protocol is also valid without (protocol_name) for forward declarations.)
@encode(type_spec)	Yields a character string that encodes the type structure of type_spec.
@"string"	Defines a constant NSString object in the current module and initializes the object with the specified 7-bit ASCII-encoded string.
@synchronized()	Defines a block of code that must be executed only by one thread at a time.
bool	It takes YES /NO
'self'
‘Super’

Example code –

#include <objc/Object.h>

@interface Car:Object

{

  //For instance variables 

}

- (void)company;

@end

#include <stdio.h>

@implementation Car

- (void)company

{

        printf("BMW!\n");

}

@end

#include <stdlib.h>

int main(void)

{

        id myCar;

        myCar =[Car new];

        [myCar company];

        [myCar free];

        return EXIT_SUCCESS;

}