gistfile1.txt

// need to add destroy of internal cache on destroy...
SC.ManyArray.reopen({

    // Set up observers.
    contentDidChange: function() {
      var observedRecords = this._observedRecords;
      if (!observedRecords) observedRecords = this._observedRecords = [];
      var record, i, len;
      // If any items in observedRecords are not in content, stop observing them.
      len = observedRecords.length;
      for (i = len - 1; i >= 0; i--) {
        record = observedRecords.objectAt(i);
        if (!this.contains(record)) {
          record.removeObserver('status', this, this.notifyStatusChange);
          observedRecords.removeObject(record);
        }
      }
      // If any item in content is not in observedRecords, observe them.
      len = this.get('length');
      for (i = 0; i < len; i++) {
        record = this.objectAt(i);
        if (!observedRecords.contains(record)) {
          record.addObserver('status', this, this.notifyStatusChange);
          this.invokeOnce(this.notifyStatusChange);
          observedRecords.pushObject(record);
        }
      }
    }.observes('[]'),

    notifyStatusChange: function() {
        this.notifyPropertyChange('status');
    },
    // Numerical order is a reasonable proxy for status hierarchy - most bad statuses are higher than most good statuses.
    // TODO: ...actually order the statuses
    status: function() {
        var length = this.get('length');
        var maxStatus = 0;
        for (i = 0; i < length; i++) {
            var status = this.objectAt(i).get('status');
            maxStatus = status > maxStatus ? status : maxStatus;
        }
        return maxStatus || SC.Record.EMPTY;
    }.property().cacheable()
});