Caching a Kendo UI DataSource object using localStorage

Question

I am using the Kendo UI ComboBox with an external, XML DataSource. Here's the DataSource code:

try
    {
        var csDataSrc = new kendo.data.DataSource(
        {
            transport:
        {
            read: "Data/StateList.xml",
            dataType: "xml",
            create: { cache: true }
        },
        schema:
        {
            type: "xml",
            data: "/States/State",
            model:
            {
                fields:
                {
                    id: "id/text()",
                    name: "name/text()"
                }
            }
        }
    });
    csDataSrc.read();
}
catch (err)
{
    log.error(err.message);
}

That creates the data source, here's the code that creates the kendo combobox:

$("#stateList").kendoComboBox(
{
    index: 0,
    placeholder: "Begin typing Coverage State...",
    dataTextField: "name",
    dataValueField: "id",
    filter: "contains",
    dataSource: csDataSrc,
    text: $("#hdnStateName").val(),
    value: $("#hdnStateKey").val(),
    change: function(e)
    {
        $("#hdnStateKey").val(this.value());
        $("#hdnStateName").val(this.text());
    }
});

This works really well but the data for the real list is enormous and I'd like to store it in local storage with something like this: localStorage.setItem("state_key", csDataSrc); Then when the page loads instead of building and reading from the server side xml all the time, I'd like for it to be something like this:

var csDataSrc = localStorage.getItem("state_key");
if(csDataSrc === null)
{
    // create the data source with the above code
    // and store it in localStorage.
}

Then bind it here...

...kendoComboBox(
{
    ...,
    .dataSource: csDataSrc,
    ...
});

I create the data source fine, it seems to store correctly in localStorage but when you leave the page and come back the data source is always null. I can see it using the resources tab of the Chrome developer tools but it won't bind to the combo box correctly. Any help or if I need to elaborate on anything to make this clearer please let me know

Thanks -s

Answer 1

To achieve that you can use a custom read method (link).

transport: {
    read: function(operation) {
        var cashedData = localStorage.getItem("moviesData");

        if(cashedData != null || cashedData != undefined) {
            //if local data exists load from it
            operation.success(JSON.parse(cashedData));
        } else {
            $.ajax({ //using jsfiddle's echo service to simulate remote data loading
                url: '/echo/json/',
                type: "POST",
                dataType: "json",
                data: {
                    json: JSON.stringify(data)
                },
                success: function(response) {
                    //store response
                    localStorage.setItem("moviesData", JSON.stringify(response));
                    //pass the pass response to the DataSource
                    operation.success(response);
                }
            });
        }                 
    }
}

Here is a working example: http://jsfiddle.net/LnTe7/12/