Objective-C Polymorphism

#import <Foundation/Foundation.h>

@interface Shape : NSObject

{

  CGFloat area;

}

-(void)printArea;

-(void)calculateArea;

@end

@implementation Shape

-(void)printArea {

 NSLog(@"The area is %f",area);

}

-(void)calculateArea {

}

@end

@interface Square : Shape

{

  CGFloat length;

}

-(id)initWithSide : (CGFloat)side;

-(void)calculateArea;

@end

@implementation Square 

-(id)initWithSide : (CGFloat)side {

 length = side;

 return self;

}

-(void)calculateArea {

 area = length * length;

}

-(void)printArea {

 NSLog(@"The area of square is %f", area);

}

@end

@interface Rectangle : Shape

{

 CGFloat length;

 CGFloat breadth;

}

-(id)initWithLength: (CGFloat)rLen andBreadth:(CGFloat)rBreadth;

@end

@implementation Rectangle

-(id)initWithLength: (CGFloat)rLen andBreadth:(CGFloat)rBreadth {

 length = rLen;

 breadth = rBreadth;

 return self;

}

-(void)calculateArea {

 area = length * breadth;

}

-(void)printArea {

 NSLog(@"The area of Rectangle is %f", area);

}

@end

int main(int ar, const char * argv[])

{

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init];

  Shape *square = [[Square alloc]initWithSide:4.2];

  [square calculateArea];

  [square printArea];

  Shape *rect = [[Rectangle alloc]initWithLength:7.88 andBreadth:6.35];

  [rect calculateArea];

  [rect printArea];

  [pool drain];

  return ;

}