just remove those 2 for DataView
I don't think anybody will use them for DataView
Igor Vaynberg wrote:
Gili,
All you would be doing is factoring out semantic incompatibilities into the
strategy interface/impls. In a way the old pageabledataview was a navigation
strategy for the regular dataview. Please try to understand the problem. Let
me lay it out for you:
The dataview class has setFirstIndex() and setViewSize() methods.
The pagabledataview extends the dataview and so inherits those, alongside
introducing the setCurrentPage()/setRowsPerPage().
The problem is that setFirstIndex() and setViewSize() do not make sense in
the pageable subclass. What does setViewSize(5) mean when you already called
setRowsPerPage(10)??? What does setFirstIndex(10) mean when you called
setCurrentPage(5)?
That's the problem. It has nothing to do with design patterns and java 101
lessons.
Currently when paging is enabled setFirstIndex() and setViewSize() will
throw an illegalstateexception which makes perfect sense to me, you
shouldn't call those if you enabled paging. Also setCurrentPage() will throw
the same exception when called while paging is disabled.
What we are discussing is simply removing setFirstIndex() and setViewSize()
because with paging built in they are not that useful. You lose some
flexibility, but not too much.
Maybe now that all the research is laid out for you you can post some
meaningful comments.
-Igor
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Gili
Sent: Sunday, September 04, 2005 11:27 AM
To: wicket-user@lists.sourceforge.net
Subject: Re: [Wicket-user] PageableGridDataView
It sounds to me like you might be able to use the
Strategy design pattern here. Your design (mentioned in a
previous email) made a lot more sense to me than Igor's idea
of throwing "unsupported" exceptions.
In essense, you could say there are two available navigation
strategies so far: linear and page-oriented. Then you simply
allow users to plug them in and everything should (hopefully)
be clean from inheritance point of view.
Gili
Christian Essl wrote:
On Fri, 02 Sep 2005 18:04:31 -0400, Gili
<[EMAIL PROTECTED]> wrote:
What is the reason? The new method sounds very anti-OOP to me.
Usually one layers functionality using interfaces.
Stuffing them all
into the base class but having them throw exceptions when
"disabled"
sounds a lot like a flat object model to me.
The reason for unifying them in one base class is also to make the
inheritance hierarchy smaller, less deep and more
consistent. If you
split DataView and PageableDataView than you also have to make a
GridDataView and a PageableGridDataView. Two classes which
are from the
hierarchy total unreleated but are otherwise more or less the same.
Further if you look at the old code of DataView and
PagabeableDataView
the PageableDataView is not easy to understand, because you have to
consider two classes with all the protected and overriding
co-work. A
general problem with inheritance, which gets worse the deeper the
hierarchy is.
And last but most important the user has to learn two classes where
there always remains some uncertainty wheter the
child-class does indeed
behave like the super class, because it could always override some
methods (as it currently does).
So I am realy for merging them in one class.
Christian
Gili
Johan Compagner wrote:
that is something we had.. and want to get rid of i think..
johan
Gili wrote:
Igor Vaynberg wrote:
Yes the support delegate is lazily created.
Setcurrentpage() throws
illegalstateexception if paging is disabled.
Sounds like an anti-pattern to me. Why don't you have a base
class without Pagable support and a subclass that is Pagable
(always) with these methods.
Gili
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