Question

I have two classes, named Parent and Child, as below. Parent is the superclass of Child I can call a method of the superclass from its subclass by using the keyword super. Is it possible to call a method of subclass from its superclass?

Child.h

#import <Foundation/Foundation.h>
#import "Parent.h"

@interface Child : Parent {

}

- (void) methodOfChild;

@end

Child.m

#import "Child.h"

@implementation Child

- (void) methodOfChild {

    NSLog(@"I'm child");

}

@end

Parent.h:

#import <Foundation/Foundation.h>

@interface Parent : NSObject {

}

- (void) methodOfParent;

@end

Parent.m:

#import "Parent.h"

@implementation Parent

- (void) methodOfParent {

    //How to call Child's methodOfChild here?

}

@end

Import “Parent.h” in app delegate’s .m file header.

App delegate’s application:didFinishLaunchingWithOptions: method..

Parent *parent = [ [Parent alloc] init];

[parent methodOfParent];

[parent release];

Answer 1

You can, as Objective C method dispatch is all dynamic. Just call it with [self methodOfChild], which will probably generate a compiler warning (which you can silence by casting self to id).

But, for the love of goodness, don’t do it. Parents are supposed to provide for their children, not the children for their parents. A parent knowing about a sub-classes new methods is a huge design issue, creating a strong coupling the wrong way up the inheritance chain. If the parent needs it, why isn’t it a method on the parent?