DWT event handling

[Lester L. Martin II]

Frank Benoit Wrote:

> bobef schrieb:
> > void handleTextEvent (Event e, Composite composite, TreeItem item, TreeEditor editor,Text text, int inset ) 
> > 
> > This is longer to write than new class {blah blah} :)
> 
> No, the additional arguments make the delegate a closure. If you would 
> write that as a anonymous class it would look like that:
> 
> In Java final vars are accessible for the anonymous class after the 
> surrounding method ends:
> 
> final Text text = ...
> final TreeEditor editor = ...
> 
> Listener l = new Listener {
>      public void handleEvent( Event e ){
>          // use text, editor as you want
>      }
> }
> 
> In D1, this would create crashes. The workaround is, to create explicit 
> member variable in the anonymous class. This is really ugly and very 
> tedious and error-prone.
> 
> Listener l = new class( composite, item, editor, text, inset ) Listener {
>      Composite composite_;
>      TreeEditor editor_;
>      Text text_;
>      int inset_;
>      public this( Composite a, TreeItem b, TreeEditor c,Text d, int e ) {
>          this.composite_ = a;
>          this.editor_ = b;
>          this.text_ = d;
>          this.inset_ = e;
>      }
>      public void handleEvent( Event e ){
>          // use the test_, editor_ ...
>          // underscore to clearly separate them from
>          // the variable used in the surounding method
>      }
> }
> 
> Now you see what is the advantage of the dgListener?
> 

In our code we just created a class that accepted a delegate. This class inherited Listener. It defined a generic event handler  that it would use if no event delegate was passed to it. What are the advantages of this template over such a design (If you need real code will post).

Lester L.  Martin II