在ASP.NET MVC中使用Knockout实践04，控制View Model的json格式内容

通常，需要把View Model转换成json格式传给服务端。但在很多情况下，View Model既会包含字段，还会包含方法，我们只希望把字段相关的键值对传给服务端。

先把上一篇的Product转换成json格式，通过pre元素显示出来。

<input data-bind="value: name"/><hr/>
<select data-bind="options: categories, value: category" ></select><hr/>
<pre data-bind="text: ko.toJSON($root, null, 2)"></pre>
@section scripts
{
    <script src="~/Scripts/knockout-2.2.0.js"></script>
    <script type="text/javascript">
        $(function() {
            $.getJSON('@Url.Action("GetFirstProduct","Home")', function (data) {
                product.name(data.Name);
                product.category (data.Category);
            });
        });
        var categories = ["小说", "散文", "传记"];
        var Product = function (data) {
            data = data || {};
            this.name = ko.observable();
            this.category = ko.observable();
            this.categories = categories;
            this.origionData = data;
            this.initialize(data);
        };
        ko.utils.extend(Product.prototype, {
            initialize: function(data) {
                this.name(data.name);
                this.category(data.category);
            },
            revert: function() {
                this.initialize(this.origionData);
            }
        });
        var product = new Product({
            name: "默认值",
            category: "传记"
        });
        //绑定
        ko.applyBindings(product);
    </script>
}

可是，我们只想把name，category键值对传给服务端，该如何做到呢？

□ 方法一

ko.toJSON()方法的第二个参数中注明要转换成json格式的键。

<pre data-bind="text: ko.toJSON($root, ['name','category'], 2)"></pre>

□ 方法二

ko.toJSON()方法的第二个参数用扩展方法。

<input data-bind="value: name"/><hr/>
<select data-bind="options: categories, value: category" ></select><hr/>
<pre data-bind="text: ko.toJSON($root, replacer, 2)"></pre>
@section scripts
{
    <script src="~/Scripts/knockout-2.2.0.js"></script>
    <script type="text/javascript">
        $(function() {
            $.getJSON('@Url.Action("GetFirstProduct","Home")', function (data) {
                product.name(data.Name);
                product.category (data.Category);
            });
        });
        var categories = ["小说", "散文", "传记"];
        var Product = function (data) {
            data = data || {};
            this.name = ko.observable();
            this.category = ko.observable();
            this.categories = categories;
            this.origionData = data;
            this.initialize(data);
        };
        ko.utils.extend(Product.prototype, {
            initialize: function(data) {
                this.name(data.name);
                this.category(data.category);
            },
            revert: function() {
                this.initialize(this.origionData);
            },
            replacer: function(key, value) {
                if (!key) {
                    delete value.categories;
                    delete value.origionData;
                }
                return value;
            }
        });
        var product = new Product({
            name: "默认值",
            category: "传记"
        });
        //绑定
        ko.applyBindings(product);
    </script>
}

以上，添加了一个扩展方法replacer，把Product的方法等剔除在json格式内容之外。

□ 方法三：重写toJSON方法

<input data-bind="value: name"/><hr/>
<select data-bind="options: categories, value: category" ></select><hr/>
<pre data-bind="text: ko.toJSON($root, null, 2)"></pre>
@section scripts
{
    <script src="~/Scripts/knockout-2.2.0.js"></script>
    <script type="text/javascript">
        $(function() {
            $.getJSON('@Url.Action("GetFirstProduct","Home")', function (data) {
                product.name(data.Name);
                product.category (data.Category);
            });
        });
        var categories = ["小说", "散文", "传记"];
        var Product = function (data) {
            data = data || {};
            this.name = ko.observable();
            this.category = ko.observable();
            this.categories = categories;
            this.origionData = data;
            this.initialize(data);
        };
        ko.utils.extend(Product.prototype, {
            initialize: function(data) {
                this.name(data.name);
                this.category(data.category);
            },
            revert: function() {
                this.initialize(this.origionData);
            },
            toJSON: function() {
                delete this.categories;
                delete this.origionData;
                return this;
            }
        });
        var product = new Product({
            name: "默认值",
            category: "传记"
        });
        //绑定
        ko.applyBindings(product);
    </script>
}