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From "Stephen Colebourne" <scolebou...@eurobell.co.uk>
Subject Re: [Collections][SUBMIT] TypedList
Date Tue, 23 Apr 2002 21:46:39 GMT
OK, this is a different design to one using Predicate, although obviously a
similar purpose. Before I can continue and finish the other collections, I
would like a decision on which way to go ;-)

This design gives much more power, but is therefore more complex (more
methods, more choice). Maybe there is a case for both. Maybe there is a case
for wrapping a Predicate in a CollectionFilter. Not quite sure yet.

I would suggest the following interface is necessary to fully express the
possibilities:
public interface CollectionFilter {
  // predicate
    public boolean allowUpdate(Object obj, Collection coll);
 // transform
    public Object beforeUpdate(Object obj, Collection coll);
 // info
    public void afterUpdate(Object obj, Collection coll);

  // predicate
    public boolean allowGet(Object obj, Collection coll);
 // info ???
    public void beforeGet(Object obj, Collection coll);
 // transform
    public Object afterGet(Object obj, Collection coll);

  // predicate
    public boolean allowRemove(Object obj, Collection coll);
 // ???
    public Object beforeRemove(Object obj, Collection coll);
 // ???
    public Object afterRemove(Object obj, Collection coll);
 }

Hmm. Having sketched that out, I think I'm tending towards keeping it simple
and sticking with PredicateList and TransformList. Views? I need guidance on
this one before I can continue.

Stephen

From: Henri Yandell <bayard@generationjava.com>
> public interface CollectionFilter {
>
>     public Object beforeAdd(Object obj, Collection coll);
>
>     public Object beforeRemove(Object obj, Collection coll);
>     public Object afterRemove(Object obj, Collection coll);
>
> }
>
>
> And same (ish) for Map? And then List/Set extend Collection filter and add
> events?
>
> When something is added to the collection, it checks with beforeAdd,
> passing the object and the collection. In TypedFilter it is set to only
> allow Strings. It finds out the object isn't a String and returns null?
>
> But does that mean return or insert null. Can we have an interface that
> means both Predicate and Transform?? Or should they be separate.
>
> Hen
>
> > So we need something more than the existing Predicate/Transformer
classes
> > then? I think I need to go and code something to it working...
> > Stephen
>
>
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