动态调整grid编辑器

cm.getCellEditor= function(a,b){
       var editor=cm.config[a].editor;
       var rowdata=grid.store.getAt(b).data;
      if(a==3) {
       if(rowdata.elementtype=="MD_Instance" ){
             return treeeditor;
       }    else  if(rowdata.elementtype=="MD_classifier" ){
           return Classfiertreeeditor ;
       }else
       return     elementId
      }
       else return editor
   }