敲出映射JSON更新现有视图模型

I have this JSON data coming from the server:

这个JSON数据来自服务器:

{"HaveNotification":false,"IsError":false,"Title":null,"Description":null}

and am trying to populate this view model via ko.mapping:

我正在尝试通过ko.mapping来填充这个视图模型:

var notifyVM = {
  HaveNotification: ko.observable(true),
  IsError: ko.observable(false), 
  Title: ko.observable('Title goes here'), 
  Description: ko.observable('Description goes here'), 
}

with this code, which is called on a polling interval:

使用此代码，在轮询间隔中调用:

function pollNotifications() {

  $.getJSON('@Url.Action("GetNotifications", "Home")', function (data) {

    ko.mapping.fromJSON(data, notifyVM);

    setTimeout(pollNotifications, 10000);
  });
}

and this is page load code:

这是页面加载代码:

$(function () {

  ko.applyBindings(notifyVM);

  setTimeout(pollNotifications, 10000);
});

but its not working. If I inspect the view model after the fromJSON call the observables are not updated, they are still at their initial values.

但它不工作。如果我在fromJSON调用后查看视图模型，那么它们仍然是初始值。

UPDATE: Some more info... if I do this in the pollNotifications function

更新:更多信息…如果我在pollnotification函数中这样做。

var newVM = ko.mapping.fromJSON(data);

I notice that the view model it creates is not the same as my one, it consists of a single observable function, whereas mine is an object with a set of observable properties.

我注意到它创建的视图模型与我的模型不同，它由一个可观察的函数组成，而我的模型是一个具有一系列可观察属性的对象。

3 个解决方案

#1

Try:

试一试:

ko.mapping.fromJS(data, {}, notifyVM);

The two parameter form expects a view-model that was previously created with ko.mapping.fromJS. If it doesn't find one (based on looking for a specific property that fromJS adds), it assumes you're calling the fromJS(data, options) form.

The 3 parameter form removes this ambiguity.

这两个参数表单期望一个之前由ko.mapp.fromjs创建的视图模型。如果没有找到(基于查找fromJS添加的特定属性)，则假定您正在调用fromJS(数据、选项)表单。3参数形式消除了这种模糊性。

#2

Have you tried manually mapping the values to the view model and seeing if that works, like this?

您是否尝试过手动地将值映射到视图模型并查看它是否有效，比如这样?

function pollNotifications() {
    $.getJSON('@Url.Action("GetNotifications", "Home")', function (data) {
        notifyVM.HaveNotification(data.HaveNotification);
        notifyVM.IsError(data.IsError);
        notifyVM.Title(data.Title);
        notifyVM.Description(data.Description);

        setTimeout(pollNotifications, 10000);
    });
}

If the above does not work, then you know it is an issue with your data; otherwise the mapping is not happening correctly with ko.mapping.fromJSON().

如果上述方法不起作用，那么您就知道这是您的数据的问题;否则，在ko.mapp . fromjson()中映射不会正确地发生。

#3

You should use ko.mapping.fromJS instead of ko.mapping.fromJSON because $.getJSON is returning a data object (not an json string):

应该使用ko.mapp . fromjs而不是ko.mapp . fromjson，因为是$。getJSON返回的是一个数据对象(不是json字符串):

The success callback is passed the returned data, which is typically a JavaScript object or array as defined by the JSON structure and parsed using the $.parseJSON() method. It is also passed the text status of the response.

返回的数据通常是一个JavaScript对象或数组，由JSON结构定义并使用$. parsejson()方法解析。它还传递响应的文本状态。

http://api.jquery.com/jquery.getjson/

do a console.log(data); to see the difference

做一个console.log(数据);看到的区别

#1