Disabling checkbox using KnockoutJS

Question

I am unable to disable the checkbox when the length of observable array reaches a specific limit. Here is the link to code : http://jsfiddle.net/pLNdc/59/

<ul class="options" data-bind="foreach: choices">
<li><label><input type="checkbox" name="NotifyMembers"
    data-bind="attr: { value: $data },
               checked: $parent.selectedChoices,
               enable: $parent.selectedChoices.length < 2" />
    <span data-bind="text: $data"></span></label></li>
</ul>
<hr />

var viewModel = {};

viewModel.choices = ["one", "two", "three", "four", "five"];
viewModel.selectedChoices = ko.observableArray(["two", "four"]);

viewModel.selectedChoicesDelimited = ko.dependentObservable(function () {
    return viewModel.selectedChoices().join(",");
});

ko.applyBindings(viewModel);

Thanks.

Answer 1

Since selectedChoices is an observable, you need to call it with parens before accessing its length property, like this:

<input type="checkbox" name="NotifyMembers"
       data-bind="attr: { value: $data },
                  checked: $parent.selectedChoices,
                  enable: $parent.selectedChoices().length < 2" />