JQuerybUI datepicker () with dynamic knockout loop

Question

I have this boilerplate knockout loop:

<div id="accordion" data-bind="jqAccordion:{},template: {name: 'task-template',foreach: Tasks,afteradd: function(elem){$(elem).trigger('valueChanged');}}">.   </div> 

<script type="text/html" id="task-template">
     <div data-bind="attr: {'id': 'Task' + TaskId}" class="group">
          <h3><b><input name="TaskName" data-bind="value: TaskName  /></b></h3>
          <p>
             Due Date: <input class="datepicker" data-bind="myDatepicker : {}, value: taskDueDate" />
          </p>
     </div>
</script>

Where datepicker is a jQuery Ui datepicker function:

ko.bindinghandler.myDatepicker =  $(function() {
    init: function( element, valueAccessor) {

        $(element).datepicker({
           changeMonth: true,
           changeYear: true
        });
    }), 
    etc.
}

why doesn't it work?

Symptoms: showing the calendar and widget respond to my interactions, but the date does not return to the input field. Any clues?

Thank you in advance!

Answer 1

You need to bind some viewModel attribute to the datepicker binding ... You overdo this part.

But you need to do some special handling when the datepicker changes the value of the element, because otherwise it will ruin the way when the knockout usually catches the change.

Set up a binding like this ...

HTML:

<div id="accordion" data-bind="jqAccordion:{},template: {name: 'task-template',foreach: Tasks,afteradd: function(elem){$(elem).trigger('valueChanged');}}">.   </div> 

<script type="text/html" id="task-template">
     <div data-bind="attr: {'id': 'Task' + TaskId}" class="group">
          <h3><b><input name="TaskName" data-bind="value: TaskName  /></b></h3>
          <p>
             Due Date: <input class="datepicker" data-bind="myDatepicker : taskDueDate" />
          </p>
     </div>
</script>

:

ko.bindingHandlers.myDatepicker =  {
    init: function(element, valueAccessor) {
        var unwrappedObs = valueAccessor();
        $(element).val(ko.unwrap(unwrappedObs));
        $(element).datepicker({
           changeMonth: true,
           changeYear: true
        });
        ko.utils.registerEventHandler(element, "change", function () {
            var unwrappedObs = valueAccessor(),
            val = $(element).datepicker("getDate");
            unwrappedObs(val);
        });
    } 
};

: http://jsfiddle.net/brettwgreen/nmb6c6gq/