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有没有办法在 Knockout JS 中实现主/从类型依赖的可观察量

发布于 2024-12-12 13:14:23 字数 302 浏览 0 评论 0原文

我的模型中有 2 个具有主/从类型关系的字段。

如果主站更新，从站也应该进行更新。

如果从站更新，主站不受影响。

我已经设法通过手动订阅来实现这一点 - http://jsfiddle.net/ProggerPete/XNUPj/

但我想知道是否可以在不手动绑定的情况下获得相同的结果。我想要它的原因是我不想在销毁视图时取消绑定我的手动订阅。

干杯，彼得

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弃爱 2024-12-19 13:14:23

一般来说，我会说手动订阅是解决您的问题的最直接的方法。

然而，创建您自己的自定义 Observable 非常容易，它封装了此功能并在可写的 dependentObservable 中处理主站和从站的更新。它可能看起来像这样：

function customObservable(initialValue) {
    var _source = ko.observable(initialValue),
        _local = ko.observable(initialValue),
        result = ko.dependentObservable({
            read: _source,
            write: function(newValue) {
               _source(newValue);
               _local(newValue); 
            }
        });

    result.local = _local;

    return result;
}

你会这样使用它：

var viewModel = {
    source: customObservable("sourceValue")
};

customObservable（无论你想怎么称呼它）都会返回一个可写的 dependentObservable，它将更新你可以作为 source 绑定的两个值。本地值也公开为 source.local。

因此，您可以在您的场景中使用它，例如： http://jsfiddle.net/rniemeyer/67pDS/

但我不确定您想如何使用此功能。如果您正在寻找接受/取消对可观察对象的编辑的能力，那么您可能需要查看此自定义可观察值。

显示自定义绑定中的处理的片段：

        var subscription = oComboBoxModel.value.subscribe(updateBestMatchFromValue, oComboBoxModel);

        //handle disposal (if ko.cleanNode is called on the element)
        ko.utils.domNodeDisposal.addDisposeCallback(element, function(){
              subscription.dispose();
        });

Generally, I would say that the manual subscription is the most straightforward approach to your question.

However, it is pretty easy to create your own custom observable that encapsulates this functionality and handles updating both the master and slave in a writeable dependentObservable. It might look something like this:

function customObservable(initialValue) {
    var _source = ko.observable(initialValue),
        _local = ko.observable(initialValue),
        result = ko.dependentObservable({
            read: _source,
            write: function(newValue) {
               _source(newValue);
               _local(newValue); 
            }
        });

    result.local = _local;

    return result;
}

and you would use it like:

var viewModel = {
    source: customObservable("sourceValue")
};

The customObservable (call it whatever you want) returns a writeable dependentObservable that will update both values that you can bind against as source. The local value is also exposed as source.local.

So, you would use this in your scenario like: http://jsfiddle.net/rniemeyer/67pDS/

I am not sure how you want to use this functionality though. If you are looking for the ability to accept/cancel edits to an observable, then you might want to look at this custom observable.

Snippet to show disposal in custom binding:

        var subscription = oComboBoxModel.value.subscribe(updateBestMatchFromValue, oComboBoxModel);

        //handle disposal (if ko.cleanNode is called on the element)
        ko.utils.domNodeDisposal.addDisposeCallback(element, function(){
              subscription.dispose();
        });

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