Inheritance in Objective C can be done by Subclassing. Here is an example of inheritance that works in objective-c.

 
**In Rectangle.h**
@interface Rectangle: NSObject

@property (nonatomic) int width;
@property (nonatomic) int height;

-(Rectangle*) initWithWidth: (int) w height: (int) h;
-(void) setWidth: (int) w height: (int) h;
-(void) print;

@end

**In Rectangle.m**

#import "Rectangle.h"
#import <`stdio.h`>

@implementation Rectangle

@synthesize width = _width;
@synthesize height = _height;

-(Rectangle*) initWithWidth: (int) w height: (int) h {
    self = [super init];
    if ( self ) {
        [self setWidth: w height: h];
    }
    return self;
}
-(void) setWidth: (int) w height: (int) h {
    self.width = w;
    self.height = h;
}
-(void) print {
    printf( "width = %i, height = %i", self.width, self.height );
}

@end

Inherit from Parent

**In Square.h**

@interface Square: Rectangle


Square.h

#import "Rectangle.h"

@interface Square: Rectangle
-(Square*) initWithSize: (int) s;
-(void) setSize: (int) s;
-(int) size;
@end

**In Square.m**

#import "Square.h"

@implementation Square
-(Square*) initWithSize: (int) s {
    self = [super init];

    if ( self ) {
        [self setSize: s];
    }

    return self;
}

-(void) setSize: (int) s {
    self.width = s;
    self.height = s;
}

-(int) size {
    return self.width;
}

@end

Import both files i.e, Rectangle.h and Square.h on top and write the below mentioned function *In your implementation .m file * where you want to use inheritance.

- (void)inheritanceExample
{
    Rectangle *rec = [[Rectangle alloc] initWithWidth: 10 height: 20];
    Square *sq = [[Square alloc] initWithSize: 15];

    // print em
    printf( "Rectangle: " );
    [rec print];
    printf( "\n" );

    printf( "Square: " );
    [sq print];
    printf( "\n" );

    // update square
    [sq setWidth: 20];
    printf( "Square after change: " );
    [sq print];
    printf( "\n" );
}

@end

*Happy Coding :)