How to do method overriding in Object-C - objective-c

Question

I am trying to do a class extension and calling the extended method from a generic method. I'm just wondering if it's possible to do it? Below is my code.
ClassA.h:
#interface ClassA : NSObject
-(void) method;
ClassA.m:
#import "ClassA.h"
-(void) method{
NSLog(#"do A");
}
ClassB.h:
#interface ClassB : ClassA
-(void) method;
ClassB.m:
#import "ClassB.h"
-(void) method{
NSLog(#"do B");
}
and in MainClass.m
-(void) doMethod {
ClassA *class = [[ClassB alloc] init];
[class method];
}
I tried to do something like this, but nothing was print out. Is it possible to do this? and will it print out "do B"??

Answer 1

Your code compiles and runs fine (minus a small typo in #interface ClassA.h that should be #interface ClassA):
cristi:tmp diciu$ cat test.m
#import <Cocoa/Cocoa.h>
#interface ClassA : NSObject
- (void) method;
#end
#interface ClassB : ClassA
-(void) method;
#end
#implementation ClassA
-(void) method{
NSLog(#"do A");
}
#end
#implementation ClassB
-(void) method{
NSLog(#"do B");
}
#end
int main()
{
ClassA *class = [[ClassB alloc] init];
[class method];
}
cristi:tmp diciu$ gcc test.m -framework Cocoa
cristi:tmp diciu$ ./a.out
2012-06-21 15:04:22.652 a.out[14408:707] do B
Apple's Objective-C docs contain a chapter on how inheritance works that is available online here.