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Creating an auto-caching Data Store in Sencha Touch and Ext JS 4

Here’s a flexible auto-caching data store.
Develop it using Sencha Architect.
1) Add a Store to your project
2) In the project inspector, click the [+] adjacent to functions to define the constructor, isCacheMiss, setCacheExpiration, and applyLocalStorageProxy functions.
3) To define the configs (remoteProxy, localStorageProxy, etc), type the name:value pairs directly into the Config panel’s search box and press the Add button. Once the property has been added to the config panel, you can click on the button to the left of the config property to set its data type (string, object, array)

Data read in from a remote proxy is automatically saved out into localstorage.
Two different caching schemes are supported.

//
// Auto-caching store. Auto-caches data in localstorage.
//

// Scenario 1: Usage with time-based caching:
// Cache data for 1 day
//
// Ext.create('MyApp.store.CachedStore', {
//   extend: 'MyApp.store.LocalCache',
//   storeId: 'PatientEdReports',
//   proxy: {
//     type: 'ajax',
//     url: 'data/mydata.json'
//   },
//   strategy: {
//    type: 'timeout',
//    duration: {'d' : 1}
//   }
// });
//

//
// Scenario 2: Usage with token-based caching
// Cache until lastUpdated token changes
//
// Ext.create('MyApp.store.CachedStore', {
//   extend: 'MyApp.store.LocalCache',
//   storeId: 'PatientEdReports',
//   proxy: {
//     type: 'ajax',
//     url: 'data/mydata.json'
//   },
//   lastUpdated: '2013-02-10 08:00:00 -08:00'
// });
//

Ext.define('MyApp.store.LocalCache', {
 extend: 'Ext.data.Store',

 requires: [
   'Ext.device.Connection',
   'Ext.data.proxy.LocalStorage',
   'Ext.DateExtras'
 ],

 config: {
   remoteProxy: { },
   localStorageProxy: { },
   lastUpdated: '2013-04-02 06:36:00 -8:00',
   strategy: { type: 'token' },
   storeId: 'MyStore'
 },

 constructor: function(config) {
   this.callParent(arguments);

   this.expireField = Ext.app.Application.appInstance.getName() + "-" + this.getLocalStorageProxy().id + '-lastupdated';

   if (Ext.Object.getSize(this.getRemoteProxy()) == 0)
    this.setRemoteProxy(this.getProxy().getInitialConfig());

   // todo - sync when browser comes online
   // note that this event doesn't fire in desktop browser
   // Ext.device.Connection.on('onlinechange',this.setConnection, this);
 },

 load: function(options, scope) {
  var online = Ext.device.Connection.isOnline();

  var me = this;
   
  if (online && this.isCacheMiss()) {
    this.setProxy(this.getLocalStorageProxy());

    // load from localstorage
    this.callParent([{
     scope: this,
     callback: function() {
       // delete from local storage
       this.removeAll();
       this.sync();

       // load from server
       this.setProxy(this.getRemoteProxy());

       // get pointer to superclass load method
       // note that this.callParent() will not work
       // from this context

       var  method=this.callParent.caller;
       var loader = method.$owner.superclass[method.$name];

       // invoke super.load() and write remote data to localstorage
       loader.call(this,{
          scope: this,
          callback: function(records,operation,success) {
            me.setProxy(this.getLocalStorageProxy());
            for (var i=0; i
              records[i].setDirty();
            }             
            me.sync(); // write to localstorage
            me.setCacheExpiration();

            // perform optional final callback
            options = options || {};

            if (Ext.isFunction(options)) {
              options = {
               callback: options,
               scope: scope || this
              };
             }

            if (options.callback) {
              options.callback.call(options.scope,
                                    records,
                                    operation,
                                    success
              );
            }
        } // callback
      }); // load
     } 
    }]);

   } else {
     this.setProxy(this.getLocalStorageProxy());
     this.callParent(arguments);
   }
}, // end function


 isCacheMiss: function() {
    // use date as a default
    var expiry = window.localStorage.getItem(this.expireField);
    if (expiry === null) {
      return true;
    }

    switch(this.getStrategy().type) {
     case 'token' :
       return !(expiry == this.getLastUpdated());

     case 'timeout' :
       var timeout = Ext.Date.parse(expiry,"Y-m-d H:i:s P");
       return (new Date() > timeout);
    }
},


setCacheExpiration: function() {

  switch(this.getStrategy().type) {
    case 'token' :
     window.localStorage.setItem(this.expireField, this.getLastUpdated());
     break;

     case 'timeout' :
      var expireDate = new Date();
      var duration = this.getStrategy().duration;
      for (var i in duration) {
        expireDate = Ext.Date.add(expireDate,i,duration[i]);
      }
      var timeout = Ext.Date.format(expireDate,"Y-m-d H:i:s P");
      window.localStorage.setItem(this.expireField, timeout);
      break;
   }
 },

 applyLocalStorageProxy: function(newObj,oldObj) {

    if (Ext.Object.getSize(newObj) == 0) {
           // set default proxy based on storeid
       newObj = {type: 'localstorage', id: Ext.app.Application.appInstance.getName() + "-" + this.getStoreId()};
       return newObj;
    } else {
      return newObj;
    }
 }
});

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