如何为淘汰赛的观测值的初始值（级联＆LT;选择＆GT;清单）？ [英] How to set initial values for Knockout's observables (for cascading <select> lists)?

问题描述

我测试了非常真棒Knockoutjs。我现在面临一个特殊的问题。

I am testing out the very awesome Knockoutjs. I am facing a peculiar problem.

我发现了一个类似的问题：<一href=\"http://stackoverflow.com/questions/6648991/knockout-js-binding-initial-default-value-of-dropdown-select-list\">Knockout JS绑定下拉列表（选择）列表的初始/默认值，但它是没有帮助，因为我的是级联列表。

I found a similar question: Knockout JS binding initial/default value of dropdown (select) list, but it is not helping, as mine are cascading lists.

我把我的initialModel如下，利用服务器的数据。

I make my initialModel as follows, using data from server.

var initialModel = @Html.Raw(JsonConvert.SerializeObject(Model)) ;

然后我定义我的ViewModel如下：

Then I define my viewModel as follows.

    var viewModel = {
    evaluationGroups :ko.observableArray(initialModel.EvaluationGroups),
    SelectedEvaluationArea:ko.observable(initialModel.selectedEvaluationArea ? initialModel.selectedEvaluationArea.Id :null ),
    SelectedEvaluationGroup :ko.observable(initialModel.selectedEvaluationGroup)
}

现在，我想级联选择列表。因此，我结合是下。

Now, I want cascading select lists. Hence my binding is as under.

<fieldset>
            <legend>Evaluation Group and Area</legend>
            <p>
                <select id="EvaluationGroupId" name="EvaluationGroupId" data-bind='options: evaluationGroups, optionsText:"Title", value:SelectedEvaluationGroup,  optionsCaption: "Select Group..."'></select>
            </p>
             <p>
                <select id="EvaluationAreaId" name="EvaluationAreaId" data-bind='options: SelectedEvaluationGroup()? SelectedEvaluationGroup().EvaluationAreas:null,  optionsValue: "Id", optionsText:"Title", value:SelectedEvaluationArea,  optionsCaption: "Select Area..."'></select>
            </p>
            </fieldset>

问题是，我无法提取我的服务器数据的初始值。如果我看到， viewModel.SelectedEvaluationGroup 的值，当页面刚刚加载，使用默认值，我看未定义。但是，如果我看到 initialModel.selectedEvaluationGroup ，它是完整的对象，符合市场预期。我究竟做错了什么？这难道不是初始化淘汰赛的观测量的正确方法是什么？

The problem is, I am unable to extract the initial value from my server data. If I see, the value of viewModel.SelectedEvaluationGroup, when the page has just loaded, with default values, I see undefined. However, if I see initialModel.selectedEvaluationGroup, it is the full object, as expected. What am I doing wrong? Is this not the correct way to initialize Knockout's observables?

推荐答案

也许你已经忘记运行applyBindings命令？

Maybe you have forgotten to run the applyBindings command?

即

ko.applyBindings(viewModel);

更新

我曾与你的jsfiddle一出戏。似乎是幸福绑定到初始值，当它被手动设置为从主阵列的。

Update

I have had a play with your jsfiddle. Seems it is happy to bind to initial values when it is manually set to ones from the main array.

http://jsfiddle.net/ZMvNM/5/

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