"Gregor Richards" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] >I ran into a situation where I needed (essentially) the visitor pattern, >but the visitor pattern sucks, so I wanted to make something like class >extensions instead (that is, methods added to a class outside of the class >definition). > > Of course, it's not possible to do this particularly cleanly, but I made a > system that works (albeit using gross string mixins). Essentially, if you > have a class A, class B : A, class C : B, you could do something like > this: > > mixin(extensions("A", "void", "doFoo", "", "")); > > mixin(extend("A", "doFoo")); > void A_doFoo(A pthis) { > /* method for A */ > } > > mixin(extend("B", "doFoo")); > void B_doFoo(B pthis) { > /* method for B */ > } > > Then if you call doFoo(new A()) the call will become A_doFoo(new A()), if > you call doFoo(new B()) the call will become B_doFoo(new B()), if you call > doFoo(new C()) the call will become B_doFoo(new C()). > > If anybody has some improvements, that'd be cool. Maybe you can get rid of > the dependence on string mixins ... but I don't think templates quite cut > it. > > - Gregor Richards >
Congrats for getting an extension-like feature into D through a simple lib. But I hope nobody (*cough* Walter) mistakes this as a sufficient substitute for real extension methods (*hint* *hint*) ;)
