Allow functions as arguments for ivh-treeview attributes/filter methods

[diimpp]

To avoid even further data massaging, it would be cool to have "virtual" attributes for id, label, children, filter by allowing function instead of attribute names.

My prime usecase is a translation array at the label property,
so my data looks like this

{id:1, children: [1,2], label: {'en_GB': 'label', 'de_DE': 'Etikett'}}

With API like this

         <div ivh-treeview="bag"
              ivh-treeview-label-attribute="label()">
         </div>

         /**
          * Get the label for `node`
          *
          * Abstracts away the need to know the actual label attribute in
          * templates.
          *
          * @param {Object} node A tree node
          * @return {String} The node label
          */
         trvw.label = function(node) {
           +++ return node[localOpts.labelAttribute()]; // Do it conditionally on function
           --- return node[localOpts.labelAttribute];
         };

And it still should be filterable. So something similar required there too.

All code snippets are only to illustrate my point, they certainly don't attempt to show way to do it.

Regards.

[jtrussell]

I think this is something we could support in version 1 by leaving those things as variables instead of functions and just watching for updates. Or perhaps better, just re-flattening our local options whenever they're asked for.

Happy to investigate when available but we'd be certainly open to a PR that doesn't break backwards compatibility.