[aspectc-user] changing the inheritance tree: adding parents to an already existing class

[Olaf Spinczyk]

Hello Peter,

Peter Vandersteegen wrote:
> Hello,
> 
> Recently I came into contact with aspectJ and its C++ counterpart: aspectC.
> In some projects I'm involved with, it can be useful to change the 
> 'inheritance tree.'
> For example I mean you can add parents to an already existing class.  
> (while using aspects of course)
> 
> Now I wonder how this can be done in aspectC.
> 
> I've found a java example to illustrate this behavior.
> In aspectJ you use " declare parents"  to change the 'inheritance tree'
> 
> public aspect FooRunnable{
>         declare parents: Foo implements Runnable;
> 
>         public void Foo.run(){
>                 System.out.prinln("added a method to an already defined 
> class");
>         }
> }
> 
> This example can also be found on: 
> http://www-106.ibm.com/developerworks/java/library/j-aopsc/
> 
> Can you please tell me if this example is done in aspectC?
> If not, can you please tell me if there are plans to include this 
> behavior in aspectC?
> 
> kind regards
> 
> Peter
> 
> ps. greet work building the aspectC language and its compiler.
> 
> 
> 
> 
> Peter Vandersteegen
> Ghent University, Dept. of Information Technology
> Sint-Pietersnieuwstraat 41, B-9000 Gent, Belgium
> WWW: http://photonics.intec.UGent.be

in AspectC++ this is called a "baseclass introduction":

#include "Runnable.h" // you need the definition of Runnable!

aspect FooRunnable {
public: // this is need to make the following intros public!
   advice "Foo": baseclass (Runnable);
   advice "Foo": void run () { ... }
};

(I didn't compile this code fragment, but it should work)

You can even go one step further in AspectC++ and define an abstract 
aspect like this:

aspect TurnIntoRunnable {
   pointcut virtual runnables() = 0;
public:
   advice runnables () : baseclass (Runnable);
   /* make only sense if all Runnables do the same ... */
   advice runnables () : void run () { ... }
};

and in a derived aspect:

aspect FooRunnable {
   pointcut runnables () = "Foo";
};

Best regards,

Olaf