/**
 * @author Ed Spencer
 * @class Ext.data.SessionStorageProxy
 * @extends Ext.data.WebStorageProxy
 * 
 * 
Proxy which uses HTML5 session storage as its data storage/retrieval mechanism.
 * If this proxy is used in a browser where session storage is not supported, the constructor will throw an error.
 * A session storage proxy requires a unique ID which is used as a key in which all record data are stored in the
 * session storage object.
 * 
 * 
It's important to supply this unique ID as it cannot be reliably determined otherwise. If no id is provided
 * but the attached store has a storeId, the storeId will be used. If neither option is presented the proxy will
 * throw an error.
 * 
 * 
Proxies are almost always used with a {@link Ext.data.Store store}:

 * 

new Ext.data.Store({
    proxy: {
        type: 'sessionstorage',
        id  : 'myProxyKey'
    }
});

 * 
 * 
Alternatively you can instantiate the Proxy directly:
 * 

new Ext.data.SessionStorageProxy({
    id  : 'myOtherProxyKey'
});
 
 * 
 * 
Note that session storage is different to local storage (see {@link Ext.data.LocalStorageProxy}) - if a browser
 * session is ended (e.g. by closing the browser) then all data in a SessionStorageProxy are lost. Browser restarts
 * don't affect the {@link Ext.data.LocalStorageProxy} - the data are preserved.
 */
Ext.data.SessionStorageProxy = Ext.extend(Ext.data.WebStorageProxy, {
    //inherit docs
    getStorageObject: function() {
        return window.sessionStorage;
    }
});

Ext.data.ProxyMgr.registerType('sessionstorage', Ext.data.SessionStorageProxy);