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With regard to parameters on components. I want to be able to pass an object
reference into a component. I'm having a few "issues" doing this.
I feel it's only right to give a reasonable amount of detail in order that
people understand the environment, so I hope that you do not mind a long
post.
This situation involves a single page called ContentManager and a component
called SimpleContentEditor. The ContentManager is capable of showing a list
of content, allowing the user to select one, and edit it. The editing itself
is done with a SimpleContentEditor component.
The object being edited is stored in a Visit object, with bean property
"currentContent". The idea is the the ContentManager page can set the visit
property to something (either an existing object, or a new one) - the
SimpleContentEditor component changes it - and then commits the object (the
content objects are Cayenne based).
My problem is that I am seeing weird behavior in the content editor - only
when Tapestry is run WITH caching (its default state). I think my problem
boils down to a misunderstanding in the way property bindings work, and when
I should make use of them etc. Hopefully someone can set me right!!!
Here's what I do currently:
The ContentManager page can display either the list, or the
SimpleContentEditor component, since it has an HTML with Conditional
components like this:
<span jwcid="modeSelect">
... other stuff here ...
</span>
<span jwcid="modeEdit">
<span jwcid="contentEditor"/>
</span>
When modeSelect is true, the content list is shown. When the user clicks to
edit content the page can setup an object in visit.currentContent, and make
it such that modeSelect would be false, and modeEdit would be true. I did
this purely so that I didn't have to create another page for the content
editor. Don't know if it's a generally bad thing or not. Anyway, onwards...
The ContentManager page binds the content editor component as follows:
<component id="contentEditor" type="SimpleContentEditor">
<binding name="content" expression='visit.currentContent'/>
<binding name="delegate" expression='beans.delegate'/>
</component>
The page is then reshown, which will show the content editor. The Component
specification for SimpleContentEditor looks like this:
<parameter
name="content"
java-type="tcdc.website.common.content.Content"
direction="custom"
required="yes">
<description><![CDATA[ A single Content instance ]]></description>
</parameter>
<component id="content" type="TextArea">
<static-binding name="columns">60</static-binding>
<static-binding name="rows">15</static-binding>
<binding name="value" expression='content.content'/>
</component>
.... (more fields exist but have been cut out for brevity)
The way I understand things, the following should happen:
1. Tapestry sets the paramters of the page up, within IBinding instances
2. The input value "content" is therefore really bound to visit.currentContent
(because of the specification on ComponentManager)
3. Tapestry will render the page using values from the object currently stored
in visit.currentContent.
4. When the page is submitted, changes in the fields will be made to the
object referenced by visit.currentContent, by the field bindings
What I observe is not quite the case. When the page renders, I get an
exception "Unable to resolve expression 'content.category' for
tcdc.dataarmour.website.components.SimpleContentEditor@1c783c5[ContentMgr/contentEditor]."
unless I change my getContent() method to:
public Content getContent() {
if (content == null) {
cat.debug("Setting up content from binding - it's currently
null");
IBinding binding = getBinding("content");
content = (Content) binding.getObject();
}
return content;
}
Then the page will show, but I get other kinds of problems when adding new
content after having editing existing content. This current email is quite
long enough, so I would first like to ask:
Is the way that I have done the binding within SimpleContentEditor correct?
I've just got a private instance "content", which has accessor methods
(getContent is shown above). setContent() just sets the var, but does not
call fireObservedChange because that causes a problem.
If you have got this far, thank you for reading this! I hope I have given
sufficient detail to get across my problem.
Regards,
Neil Clayton
(PS: If you see strange text you don't understand underneath my email, don't
worry - it's just my PGP signature)
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