Question

我想知道如何在knockout.js中创建某些字段observable，这是我从ajax调用中获得的，而不必在我的viewmodel中定义整个对象。这可能吗？以下是我到目前为止的情况：

var viewModel = {
    lines: new ko.observableArray([])
};
function refreshList(ionum) {
    var data = {};
    data['IONum'] = ionum;
    $.ajax({
    url: 'handlers/getlines.ashx',
    data: data,
    cache: false,
    dataType: 'json',
    success: function(msg) {

        viewModel.lines(msg);
        //here is where I am attempting to make the email address field observable
        /*for (var i = 0; i < msg.length; i++) {
            viewModel.lines()[i].emailAddress = new ko.observable(msg[i].emailAddress);

        }*/

        //alert(viewModel.lines[0].emailAddress);
        //ko.applyBindings(viewModel);


    }

});
}

Answer 1

使用the mapping plugin for Knockout，您可以从Ajax调用返回的普通Javascript对象定义视图模型：

var viewModel = ko.mapping.fromJS(data);
// Every time data is received from the server:
ko.mapping.updateFromJS(viewModel, data);

我的情况几乎相似，我的对象是Javascript类的实例。这些类在没有Knockout的情况下定义，我想修改它们以改为使用observable。

我创建了一个小助手，将常规对象转换为可观察对象。您可以指定可观察字段，也可以在对象（原型）中设置它们。（我想过自动执行此操作，但我无法确定哪个字段可以安全转换，哪个不是。）

(function() {
    ko.observableObject = function(object, ko_fields) {
        ko_fields = ko_fields || object._ko_fields;
        if (!ko_fields) {
            return object;
        }
        for (var f_idx = 0; f_idx < ko_fields.length; f_idx++) {
            var field_name = ko_fields[f_idx];
            if (object[field_name] && object[field_name].__ko_proto__ !== undefined) {
                continue;
            }
            if (object[field_name] instanceof Array) {
                var field_array = object[field_name];
                for (var a_idx = 0; a_idx < field_array.length; a_idx++) {
                    field_array[a_idx] = ko.observableObject(field_array[a_idx]);
                }
                object[field_name] = ko.observableArray(field_array);
            } else {
                object[field_name] = ko.observable(object[field_name]);
            }
        }

        return object;
    };
})();

您可以将它与类或普通对象一起使用。

// With classes. We define the classes without Knockout-observables
// User.subscriptions is an array of Subscription objects
User = function(id, name) {
    this.id = id;
    this.name = name;
    this.subscriptions = [];
};

Subscription = function(type, comment) {
    this.type = type;
    this.comment = comment;
});

// Create some objects
var jan = new User(74619, "Jan Fabry");
jan.subscriptions.push(new Subscription("Stack Overflow", "The start"));
jan.subscriptions.push(new Subscription("Wordpress Stack Exchange", "Blog knowledge"));
var chris = new User(16891, "Chris Westbrook");

// We would like to convert fields in our objects to observables
// Either define the fields directly:
ko.observableObject(jan, ['id', 'name', 'subscriptions']);
ko.observableObject(chris, ['id', 'name', 'subscriptions']);
// This will only convert the User objects, not the embedded subscriptions
// (since there is no mapping)

// If you define it in the class prototype, it will work for embedded objects too
User.prototype._ko_fields = ['id', 'name', 'subscriptions'];
Subscription.prototype._ko_fields = ['type', 'comment'];
ko.observableObject(jan);
ko.observableObject(chris);

// It also works with objects that are not created from a class, like your Ajax example
var observable = ko.observableObject({'id': 74619, 'name':'Jan'}, ['id', 'name']);

Answer 2

我解决了这个问题，发现在将对象设置到我的视图之前声明我的对象上的可观察字段更好，比如

for (var i=0;i<msg.lenth;i++){
msg[i].emailAddress=ko.observable(msg[i].emailAddress);
}
viewModel.lines(msg);

Answer 3

以下是我的CoffeeScript RequireJS module，用于将我称之为“查看数据”（服务器派生的JSON值）转换为KO ViewModels：

define "infrastructure/viewModels", [], (viewModels) ->
    exports = {}

    isDate = (x) ->
        typeof x is "string" and
        x.startsWith "/Date("

    deserializeDate = (dateString) ->
        new Date(parseInt(dateString.substr(6)))

    isScalar = (x) ->
        x is null or
        typeof x is "string" or
        typeof x is "number" or
        typeof x is "boolean"

    exports.fromViewData = (viewData) ->
        if isDate viewData
            return ko.observable deserializeDate viewData
        if isScalar viewData
            return ko.observable viewData

        viewModel = {}
        for own key, value of viewData
            if key is "id" then continue

            viewModel[key] = 
                if Array.isArray value
                    ko.observableArray (exports.fromViewData el for el in value)
                else
                    exports.fromViewData value

        return viewModel

    return exports

样本用法：

require ["infrastructure/viewModels"], (viewModels) ->
    $.getJSON "/url/to/data", (viewData) ->
        viewModel = viewModels.fromViewData viewData
        ko.applyBindings viewModel

当然，如果您不使用CoffeeScript，可以通过单击链接网站上的“Try CoffeeScript”来转换为JavaScript。如果您不使用RequireJS，那么只需从我的模块中获取相关函数，而不将它们包装在define中。

在knockout.js中进行ajax检索后，可以观察字段

3 个答案: