Knockout js checkbox checked binding

问题:

In knockout js am trying to perform a foreach on an array of data to display check boxes. The issue I am having is that the checked databind does not appear to run until I interact with one of the boxes. For example, below I am generating 5 text boxes none of which are showing up as checked. However when I click "one", "two" and "four" also get checked as they should have been from the beginning.

Javascript:

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);

HTML:

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

Fiddle is at: http://jsfiddle.net/bvGG3/1/

Thanks for your help.

回答1:

In Knockout before version 3.0 the bindings fired in order, so your problem is that your checked binding fires before your attr binding.

So you need to change the order of your bindings:

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

Demo JSFiddle.

Or your original code will work when you update to 3.0 (demo JSFiddle).