Ext.grid.CheckboxSelectionModel复选框设置某行不可以选中

     var sm = new Ext.grid.CheckboxSelectionModel({
        renderer:function(v,c,r){
              if(r.get("isEdit")=="可以编辑"){
                  return "<div class=\"x-grid3-row-checker\"> </div>";
              }else{
                  return "";
              }
          }
    });

var sm = new Ext.grid.CheckboxSelectionModel();

问题：Ext.grid.EditorGridPanel添加sm后无法勾选

解决：在columns里面也要添加sm