start

Fired when the read() method of Shield UI DataSource is called and before the data retrieval and processing pipeline is started. The event can be canceled using preventDefault(), in which case the data retrieval and processing pipeline will not be started.

var dataSource = new shield.DataSource({
    events: {
        start: function (e) {
            //validate data retrieval can be started
            if (!modelState.isValid()) {
                e.preventDefault();
                return;
            }

            console.log("starting data retrieval.");
        }
    }
});