Basic Objective-C
Advanced Objective-C
Objective-C Useful Resources
Selected Reading
- Command-Line Arguments
- Objective-C - Error Handling
- Objective-C - Log Handling
- Objective-C - Type Casting
- Objective-C - Typedef
- Objective-C - Preprocessors
- Objective-C - Structures
- Objective-C - Strings
- Objective-C - Pointers
- Objective-C - Arrays
- Objective-C - Numbers
- Objective-C - Blocks
- Objective-C - Functions
- Objective-C - Decision Making
- Objective-C - Loops
- Objective-C - Operators
- Objective-C - Constants
- Objective-C - Variables
- Objective-C - Data Types
- Objective-C - Basic Syntax
- Objective-C - Program Structure
- Objective-C - Environment Setup
- Objective-C - Overview
- Objective-C - Home
Advanced Objective-C
- Obj-C - Memory Management
- Objective-C - Fast Enumeration
- Obj-C - Foundation Framework
- Objective-C - Composite Objects
- Objective-C - Dynamic Binding
- Objective-C - Protocols
- Objective-C - Extensions
- Objective-C - Posing
- Objective-C - Categories
- Objective-C - Data Encapsulation
- Objective-C - Polymorphism
- Objective-C - Inheritance
- Objective-C - Classes & Objects
Objective-C Useful Resources
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
Objective-C - Typedef
Objective-C Typedef
The Objective-C programming language provides a keyword called typedef, which you can use to give a type a new name. Following is an example to define a term BYTE for one-byte numbers −
typedef unsigned char BYTE;
After this type definition, the identifier BYTE can be used as an abbreviation for the type unsigned char, for example:.
BYTE b1, b2;
By convention, uppercase letters are used for these definitions to remind the user that the type name is really a symbopc abbreviation, but you can use lowercase, as follows −
typedef unsigned char byte;
You can use typedef to give a name to user-defined data type as well. For example, you can use typedef with structure to define a new data type and then use that data type to define structure variables directly as follows −
#import <Foundation/Foundation.h>
typedef struct Books {
NSString *title;
NSString *author;
NSString *subject;
int book_id;
} Book;
int main() {
Book book;
book.title = @"Objective-C Programming";
book.author = @"TutorialsPoint";
book.subject = @"Programming tutorial";
book.book_id = 100;
NSLog( @"Book title : %@
", book.title);
NSLog( @"Book author : %@
", book.author);
NSLog( @"Book subject : %@
", book.subject);
NSLog( @"Book Id : %d
", book.book_id);
return 0;
}
When the above code is compiled and executed, it produces the following result −
2013-09-12 12:21:53.745 demo[31183] Book title : Objective-C Programming 2013-09-12 12:21:53.745 demo[31183] Book author : TutorialsPoint 2013-09-12 12:21:53.745 demo[31183] Book subject : Programming tutorial 2013-09-12 12:21:53.745 demo[31183] Book Id : 100
typedef vs #define
The #define is a Objective-C directive, which is also used to define the apases for various data types similar to typedef but with following differences −
The typedef is pmited to giving symbopc names to types only whereas #define can be used to define apas for values as well, pke you can define 1 as ONE, etc.
The typedef interpretation is performed by the compiler where as #define statements are processed by the pre-processor.
Following is a simplest usage of #define −
#import <Foundation/Foundation.h>
#define TRUE 1
#define FALSE 0
int main( ) {
NSLog( @"Value of TRUE : %d
", TRUE);
NSLog( @"Value of FALSE : %d
", FALSE);
return 0;
}
When the above code is compiled and executed, it produces the following result −
2013-09-12 12:23:37.993 demo[5160] Value of TRUE : 1 2013-09-12 12:23:37.994 demo[5160] Value of FALSE : 0Advertisements