Category in iPhone

After using inheritance, a derived class can only access those methods that existed in the base class. The derived class can't access the extended method in the category.

But after using the category, the derived class can access all the methods (existed + extended) in the derived class.

class myClass.h

@interface test : UIViewController{

}

-(NSString *) method 1;

-(NSString *) method 2;

@end

class myClass.m

@implementation{

-(NSString*) method1{

return( @"method1");

}

-(NSString *)method2{

return (@"method2");

}

}

/////

class yourClass.h

#import "myClass.h"

@interface{

...

}

class yourClass.m

@implementation{

-(void)viewdidLoad{

myClass * _myclass = [[ myClass alloc]init];

NSLog(@"%@),[_myclass method1]);

NSLog(@"%@),[_myclass method1]);

}

}

//////// Category implementation. (className +categoryName)

Step 1

Choose the Category template from the XCode new file.

Step 2

Category on the name for the super-class.

#import <Foundation/Foundation.h>

#import "myClass.h"

@interface myClass(ktest)

-(NSString *) method4;

-(NSString *) method5;

@end

#import <Foundation/Foundation.h>

#import "myClass.h"

@interface myClass(ktest)

-(NSString *) method4;

-(NSString *) method5;

@end

//// Category class.m file

#import "myClass+ktest.h"

@implementation myClass(ktest){

-(NSString *) method4{

return (@"method4");

}

-(NSString *) method5{

return (@"method5");

}

/// Category Implementation in your Derived Class

yourClass.m

#import"myClass.h"

#import "myClass+ktest.h"

@implementation{

-(void)viewdidLoad{

myClass * _myclass = [[ myClass alloc]init];

/**After Importing the "myClass+ktest.h" same object of _myClass can implement all the method i.e myClass and methods from myClass+test **/

NSLog(@"%@),[_myclass method1]);

NSLog(@"%@),[_myclass method2]);

NSLog(@"%@),[_myclass method3]);

NSLog(@"%@),[_myclass method4]);

}

}