code: function(property, value, start, anyMatch, caseSensitive){
          if(Ext.isEmpty(value, false)){
              return -1;
          }
          value = this.createValueMatcher(value, anyMatch, caseSensitive);
          return this.findIndexBy(function(o){
              return o && value.test(o[property]);
          }, null, start);
      }
docs: Finds the index of the first matching object in this collection by a specific property/value.
  @param {String} property The name of a property on your objects.
  @param {String/RegExp} value A string that the property values
  should start with or a RegExp to test against the property.
  @param {Number} [start=0] The index to start searching at.
  @param {Boolean} [anyMatch=false] True to match any part of the string, not just the beginning.
  @param {Boolean} [caseSensitive=false] True for case sensitive comparison.
  @return {Number} The matched index or -1
  @since Ext 2