Extjs 继承Ext.data.Store不起作用原因分析及解决

DocStore = Ext.extend(Ext.data.Store,{
initComponent:function(){
this.proxy = new Ext.data.HttpProxy({url:this.url});
this.reader = new Ext.data.JsonReader(
{
totalProperty: results,
root: rows,
id:docid,
fields: [docid, extention,docname, author, sizes, datecreated]
}

);
this.sortInfo = { field: datecreated, direction: DESC };
this.remoteSort = false;
DocStore.superclass.initComponent.call(this);
}
});