KnockoutJS arrayFilter doesn't update

Question

A Knockout newbie here. I've tried to use ko.utils.arrayFilter but it doesn't seem to update when I use it. I'm using the same method I used with arrayForEach so I'm not sure what's wrong here. How can I get this the list to update when using arrayFilter?

JS:

function entry(name, category) {
    this.name = ko.observable(name);
    this.category = ko.observable(category);
}

function entriesModel() {
    this.entries = ko.observableArray([]);
    this.filter = function () {
        ko.utils.arrayFilter(this.entries(), function (item) {
            return item.category == 'SciFi';
        });
    };
    this.sort = function () {
        this.entries.sort(function (a, b) {
            return a.category < b.category ? -1 : 1;
        });
    };
}

$(document).ready(function () {
    $.getJSON("entries.php", function (data) {
        entries(data);
    });
    ko.applyBindings(entriesModel());
});

HTML:

<ul data-bind="foreach: entries">
<li>
    <p data-bind="text: name"></p>

    <p data-bind="text: category"></p>
</li>

<button data-bind="click: filter">Filter</button>
<button data-bind="click: sort">Sort</button>

JSON:

[{"id":"1","name":"Iron Man","category":"SciFi"},{"id":"2","name":"Terminator","category":"SciFi"},{"id":"3","name":"The Pianist","category":"Drama"},{"id":"4","name":"The Hangover","category":"Comedy"}]

Answer 1

ko.utils.arrayFilter doesn't filter the array in place. It returns a new array with the filtered items, and leaves the original array as is.

An example of how to use ko.utils.arrayFilter is here: http://www.knockmeout.net/2011/04/utility-functions-in-knockoutjs.html

Answer 2

Not sure if this is exactly what you want, but your filter function won't do an in-place filter, so you need to reassign the observableArray with the new filtered array. Such as

this.filter = function () {
    this.entries(ko.utils.arrayFilter(this.entries(), function (item) {
        return item.category == 'SciFi';
    }));
};

See here: http://jsfiddle.net/aKfUc/1/

If you don't want to permanently change the array, you may want to use a ko.computed observable:

http://knockoutjs.com/documentation/computedObservables.html

Answer 3

data-bind="value: currentFilter, valueUpdate: 'afterkeydown'"

将解决您的问题