gistfile1.js

Ember.computed.iterativeStringFilter = function(dependentKey, propertyKey, searchKey) {
  var options = {
    initialize: function (array, changeMeta, instanceMeta) {
      instanceMeta.filteredArrayIndexes = new Ember.SubArray();
    },

    addedItem: function(array, item, changeMeta, instanceMeta) {
      var itemValue = item.get(propertyKey),
          searchValue = this.get(searchKey),
          match = itemValue.indexOf(searchValue) > -1,
          filterIndex = instanceMeta.filteredArrayIndexes.addItem(changeMeta.index, match);

      if (match) {
        array.insertAt(filterIndex, item);
      }

      return array;
    },

    removedItem: function(array, item, changeMeta, instanceMeta) {
      var filterIndex = instanceMeta.filteredArrayIndexes.removeItem(changeMeta.index);

      if (filterIndex > -1) {
        array.removeAt(filterIndex);
      }

      return array;
    },
    
    // this hook would be called for dependent properties without one-at-time semantics
    // `key` would contain the name of the key that changed
    changedProperty: function(array, key, changeMeta, instanceMeta) {
      if (key != searchKey) return;

      var searchValue = this.get(searchKey),
          // the previous value stored at this key would be stored in the changeMeta
          prevSearchValue = changeMeta.previousValue;

      // if our new search value is strictly more specific than
      // the previous, then we only need to remove items that are
      // already in the filter, instead of invalidating the entire
      // filter.
      if (searchValue.indexOf(prevSearchValue) > -1) {
        for (var i = 0; i < array.length; i++) {
           // ... remove item from filter if necesary ...
        }

        return array;
      }
      // else return undefined and recalculate the entire filter.
    }
  };

  return Ember.arrayComputed(dependentKey, options);
};