Automatic Delegation For Java

It would be very helpful if Java had a syntax to explicitly specify delegation, something in the lines of:

 public class SomeClass extends SomeSuperClass, delegates Interface in interfaceImp{
    InterfaceImp interfaceImp;
    ...
 }

-- EduardoMadrid

 public class SomeClass extends SomeSuperClass, implements Interface {
    delegate Interface to InterfaceImp interfaceImp;
    ...
 }

-- RafaelAlvarez

This has been implemented as a native Java API, though it's still in a proof-of-concept phase. It's called Delegator and can be found on http://sourceforge.net/projects/delegator/

I've currently (begin 2005) started development again as a masters thesis so more should be available in the coming months.

See DelegatorIsDelegationInJava

-- KlaasVanSchelven

If you use a good IDE like IntellijIdea, it will take a lot of the burden off your shoulders. For instance, IDEA has a feature called Delegate Methods.

But, as much as I love IntellijIdea, it would be useful not to clutter the source code with the delegation functions

PleaseComment

Shouldn't this be required too?

 public class SomeClass extends SomeSuperClass, implements Interface {
    delegate Interface to InterfaceImp interfaceImp;
    public SomeClass() { interfaceImp = new InterfaceImp(); }
    ...
 }

because I understand that the delegate keyword is meant to be a short hand for

 public class SomeClass extends SomeSuperClass, implements Interface {
    private InterfaceImp interfaceImp;
    public SomeClass() { interfaceImp = new InterfaceImp(); }
    public ReturnType interfaceMethod1(Object param1) { return interfaceImp.interfaceMethod1(param1); }
    ...
 }

So the interfaceImp has to be instantiated first.

I suppose the case for method clash can be resolved as multiple inheritance in C++, i.e. clashed methods have to be explicitly declared.

Note that Java doesn't provide a way to resolve collisions between methods from different interfaces. I find this disturbing. If methods have the same name they get the same implementation, no matter what context (interface) they are declared in.

Many years ago I thought this was a good idea. Since then I find myself rarely delegating behavior. I'm not exactly sure why. Perhaps it's a side effect of more refactoring. -- EricHodges

I'm a big fan of delegation, and concepts like DelegationInheritance; which is why AutomaticDelegation? is one of the ideas I'd like to have implemented in DefnLanguage (i.e. MyFavouriteNonexistantProgrammingLanguage?). -- KarlKnechtel

Automated Delegation is a Viable Alternative to Multiple Inheritance in Class Based Languages:

http://www.cs.virginia.edu/~evans/cs655-S00/readings/viega.pdf

CategoryAutomated