On Wed, Nov 07, 2007 at 11:31:12AM +0100, Mats Norén wrote:
>
> Is the above statement really true considering that by adding abstract
> methods to your page you defer the creation of the markup in just the
> same way as the new proposed solution?
>
> BasePage.java
>
> public BasePage() {
> addAbstract1("abstractId1");
> addAbstract2("abstractId2);
> }
>
> public abstract addAbstract1(String abstractId1);
> public abstract addAbstract2(String abstractId2);
>
>
> BasePage.html
>
> <span wicket:id="abstractId1"/>
> <span wicket:id="abstractId2"/>
>
> What is the difference between that and doing abstract / implements?
You've just illustrated one of the major problems with the
panel-from-a-subclass approach: it's easy to get it wrong. In your
example, addAbstract1 and addAbstract2 will be called in a class whose
constructor has not yet been called. Consider:
public DerivedPage extends BasePage {
private String name;
public DerivedPage(String name) {
super();
this.name = name;
}
public abstract addAbstract1(String abstractId1) {
add(new NamePanel(abstractId1, name));
}
}
This code is broken, since you're constructing NamePanel before name has
been initialized. Someone later in this thread shows a better way to do
this, by calling the overridable methods from onBeforeRender. But this
is also tricky; because onBeforeRender can be called multiple times you
must maintain a flag to ensure you only add your panels once.
Given these subtle problems with this approach, I admit I'm warming to
the multiple extend/child idea.
jk
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