code: function() {
  		var me = this,
  			field = undefined;
  
  		Ext.each(me.grid.headerCt.getGridColumns(), function(col) {
  			if (col.filter) {
  				field = me.fields.get(col.dataIndex);
  				return false;
  			}
  		});
  
  		return field;
  	}
docs: private