Coding data records is tedious if strong typing and string versions of each field are required for web_ui binding. See http://stackoverflow.com/questions/14427600/dart-best-practice-to-deal-with-data-records

The following would be one approach:
    class Item extends DataRecord {
      int itemid = 0,
      String itemName = 'New item',
      double score = 0.0;
    }
Then, without further coding, to be able to write

    item.toStrings(); // Perhaps to/from unnecessary...
    ...
    item.fromStrings(); // ... if strings version synced automagically?
    ...
    item.fromJson(json);
    ...
    item.setDefaults(); // results in {0,'New item',0.0}
And to be able to write in the HTML:

    value="{{item.strings.score}}"

A simpler alternative might be to allow value="{{}}" bindings to non-string types.