if-data.js

Handlebars.registerHelper("ifData", function(property, fn)
{
  var context = (fn.contexts && fn.contexts[0]) || this;
  var args    = [property];

  var canAction = function(can_args)
  {
    alert('I was called for '+can_args[0].get('id'));
    return true;
  };

   // Resolve actual values for all params to pass to the conditional callback
  var normalizer = function() {
    return Ember.Handlebars.resolveParams(context, args, fn);
  };
 
  return Ember.Handlebars.bind.call(context, 'content', fn, true, canAction, normalizer, args);
});

show.hbs

{{#ifData model }}
  <h1> Showme </h1>
{{/ifData}}

ifData is not reevaluated when model is modified.