问无法在我的Extjs应用程序中使用Json-Server正确执行CURD操作

EN

Ext.define('ThemeApp.store.peopleStore', {
    extend: 'Ext.data.Store',
        model: 'ThemeApp.model.peopleModel',
        storeId: 'peopleStore',
        pageSize: 500,  
        autoLoad: true,
        autoSync: true
});

Ext.define('ThemeApp.model.peopleModel', {
    extend: 'Ext.data.Model',

    fields: [ 'id' ,'title','body'],

    proxy: {
        type: 'rest',
        //format: 'json',
        limitParam:"",
        filterParam: "",
        startParam:'',
        pageParam:'',

        url:'http://localhost:3000/posts',
        api: {
    read  : 'http://localhost:3000/db',
    create: 'http://localhost:3000/posts',
    update  : 'http://localhost:3000/posts' ,
    destroy : 'http://localhost:3000/posts' 
 }, 
        headers: {'Content-Type': "application/json" },        
        reader: {
        type: 'json',
        rootProperty:'posts'
        },
        writer: {
            type: 'json'
        }           
    }
});

var UserStore = Ext.getStore('peopleStore');
var user = Ext.create('ThemeApp.model.peopleModel',{title: "Test", body: "Testing" });                      
user.save(); //POST /users
UserStore.load();

var grid =  button.up('gridpanel');
var selection = grid.getView().getSelectionModel().getSelection()[0];

if (selection) {

  UserStore.remove(selection);
  UserStore.load();                         
}