Re: I wish ResourceReference had a more general base class or interface

[Garret Wilson]

Ah, nice! That does exactly what I'm looking for---thank you very much!

Garret

On 9/3/2014 8:49 AM, Martin Grigorov wrote:

See org.apache.wicket.markup.html.image.Image#getImageResourceReference

item.add(new Image("icon") {
       @Override
       public ResourceReference getResourceReference() {
         if(item.getModelObject().isBar()) {
           return barIconResourceReference;
         } else {
           return fooIconResourceReference;
         }
       }
    }));

There is #getResource() too. Setters as well.

Martin Grigorov
Wicket Training and Consulting
https://twitter.com/mtgrigorov


On Wed, Sep 3, 2014 at 6:40 PM, Garret Wilson <gar...@globalmentor.com>
wrote:

Here are some thoughts after working with PackageResourceReference.

The IModel interface is really great. It makes no assumptions about where
things are coming from. I can even install an IModel instance I create on
the fly, just overriding IModel.getObject() (and a couple of other methods).

I am listing files in a DataView. I want each file to have an icon, loaded
from resources. The actual icon depends on the file. Here are two example
icons:

    final PackageResourceReference fooIconResourceReference = new
    PackageResourceReference(Foo.class, "foo-icon.png");
    final PackageResourceReference barIconResourceReference = new
    PackageResourceReference(Bar.class, "bar-icon.png");


In my DataVIew I'd like the actual icon to be determined at retrieval
time, whether "foo-icon.png" or "bar-icon.png", based upon
FileItem.isBar(), like this:

    item.add(new Image("icon", new IPackageResourceReference() {
       @Override
       public PackageResource getResource() {
         if(item.getModelObject().isBar()) {
           return barIconResourceReference.getResource();
         } else {
           return fooIconResourceReference.getResource();
         }
       }
    }));


See, if there was some general IPackageResourceReference interface
(analogous to IModel), I could simply override its getResource() method and
delegate to already-constructed package resource reference instance. Or
even better, if there was a general resource reference interface, then I
could just override getResourceReference() and return
fooIconResourceReference or barIconResourceReference.

But this won't work as it currently stands, because the
PackageResourceReference class makes all sorts of assumptions about how the
information would be retrieved. I suppose I could pass dummy variables to
its constructor, since I'm going to completely override its getResource()
method, but that simply underscores the need for some general interface I
could override directly.

You might ask why I just don't check my item's isBar() method up front,
and install the correct package resource reference in the image to begin
with. The answer is that I want the icon to be determined dynamically at
render time, not once when the data view is created (and perhaps not
altered for a while, even though file attributes may have changed).

I'm working around it. I just thought I'd pass this thought along as input
on future changes to Wicket.

Garret