loading a knockout.js observableArray() from .ajax

Question

This puzzles me. It must be something small I'm not seeing. I'm trying to load a very simple observableArray in knockout with an ajax call.

javascript

// we bind the array to the view model property with an empty array.
var data = [];   
var viewModel = {
    vendors: ko.observableArray(data)
};
ko.applyBindings(viewModel);

$(function () {
    // on this click event, we popular the observable array
    $('#load').click(function () {
        // WORKS. Html is updated appropriately.
        viewModel.vendors([{ "Id": "01" },{ "Id": "02" },{ "Id": "03" }]);

        // DOES NOT WORK. Fiddler2 shows the same exact json string come back 
        // as in the example above, and the success function is being called.
        $.ajax({
            url: '/vendors/10',
            dataType: 'json',
            success: function (data) {
                viewModel.vendors(data);
            }
        });
    });
});

html

<button id="load">Load</button>
<ul data-bind="template: { foreach: vendors }">
    <li><span data-bind="text: Id"></span></li>
</ul>

---

Question: Why does the successful ajax call, who's data variable value matches byte-for-byte the hard typed value, not trigger the html refresh?

Answer 1

We can use a simple JavaScript util function as a work-around.

Instead of viewModel.vendors(data);, wrapping with eval (research the dangers of eval first) will work.

eval("viewModel.vendors("+JSON.stringify(data)+");");

Answer 2

There is no reason this would not work fine. As this demonstrates.

http://jsfiddle.net/madcapnmckay/EYueU/

I would check that the ajax post is actually returning json data and that that json is an array and that it's being parsed correctly.

I had to tweak the ajax call to get the fiddle ajax handlers to work correctly.

Nothing more I can think of.

Hope this helps.

Answer 3

This is bug I think, Knockout's sample is working when we use it with wrapper class:

public class ResultWrapper
{
    public Title {get;set;}
    public List<Result> {get;set;}
}

http://learn.knockoutjs.com/#/?tutorial=webmail

But if we return Results directly there is no way to bind it. (without extra applyBindings!)

Answer 4

var self=this;
//var self first line in model

$.ajax({
            url: ",
            dataType: "json",
            contentType: 'application/json',
            type: "POST",
            data: JSON.stringify({ }),
            processdata: true,

            beforeSend: function () {
                $.mobile.loading('show');
            },

            error: function (xhr, textStatus, errorThrown) {
                alert('Sorry!');
            },

            success: function (data) {

                $.mobile.loading('hide');
                if (data.result!= '') {
                    self.vendors(data.result);



                } else {
                    self.vendors({something});

                }
            }
        });

Use self.vendors not this viewModel.vendors

Answer 5

Here is what I done in my MVC .net app with knockout and jquery.

// Scripts/groItems.js
(function () {

    var ViewModel = function () {
        items = ko.observableArray(),
            ItemName = ko.observable(),
            Img = ko.observable(),
            Qty = ko.observable()
    }

    $.getJSON('/Items2/AllItems', function (data) {
        for (var i = 0; i < data.length; i++) {
            self.items.push(data[i]);
        }
    });

    var vm = new ViewModel();

    $(function () {
        ko.applyBindings(vm);
    });

}());

@model IEnumerable<GroModel.Item>
@{
    ViewBag.Title = "Index";
}

<p>
    @Html.ActionLink("Create New", "Create")
</p>

<div data-bind="text: items().length"></div>
<table class="container table table-hover">
    <thead>
        <tr>
            <th>Item name</th>
            <th>img</th>
            <th>qty</th>
        </tr>
    </thead>
    <tbody data-bind="foreach: items">
        <tr>
            <td data-bind="text: ItemName"></td>
            <td data-bind="text: Img"></td>
            <td data-bind="text: Qty"></td>
        </tr>
    </tbody>
</table>

@section Scripts {
    <script src="~/Scripts/knockout-3.4.2.js"></script>
    <script src="~/Scripts/groItems.js"></script>
}

Following is part of my code at the Items2Controller.cs

    private GroContext db = new GroContext();
    public JsonResult AllItems()
    {
        return Json(db.Items.ToList(), JsonRequestBehavior.AllowGet);
    }

Hope this will help. Thanks