Question

我正在尝试绑定一个在内部使用可观察数组的计算observable。加载时会调用“read”方法。但是，当表中的值发生更改并移动焦点时，不会调用“write”方法。请注意，对于不包装数组而是简单字符串的简单计算的observable，“write”方法有效。但是对于这种情况，它不起作用。我查看了Knockout api文档和在线论坛，但找不到任何相关信息。有人可以请教吗？以下是HTML代码

        <thead>
        <tr><th>People Upper Case Name</th></tr>
        </thead>
        <tbody data-bind="foreach: uppercasepeople">
        <tr>
           <td ><input type="text" data-bind="value: name"/></td>            
        </tr>
        </tbody>
        </table>

以下是Java脚本代码

    <script type="text/javascript">


var MyViewModel = function () {

    var self = this;
    var self = this;

    //Original observable array is in lower case
    self.lowercasepeople = ko.observableArray([
    { name: "bert" },
    { name: "charles" },
    { name: "denise" }
]);

    //coputed array is upper case which is data-bound to the ui
    this.uppercasepeople = ko.computed({
        read: function () {
            alert('read does get called :)...yaaaa!!!');
            return self.lowercasepeople().map(function (element) {
                var o = { name: element.name.toUpperCase() };
                return o;
            });
        },
        write: function (value) {
            alert('Write does not get called :(... why?????');
            //do something with the value
            self.lowercasepeople(value.map(function (element) { return element.toLowerCase(); }));
        },
        owner: self
    });


}

ko.applyBindings(new MyViewModel());

我已将代码与Knockout API文档中显示的示例类似，以便人们轻松关联。

Answer 1

计算出的observable，你只处理数组本身。只有在您尝试直接设置write的值时才会调用uppercasepeople函数。

在这种情况下，您可能希望在person对象本身上使用可写的可计算方法，并使名称可观察。可编写的计算机然后将名称转换为大写，并且在写入时将使用小写值填充名称observable。

Answer 2

var MyViewModel = function () {

var self = this;

//Original observable array is in lower case
self.lowercasepeople = ko.observableArray([
{ name: "bert" },
{ name: "charles" },
{ name: "denise" }
]);

self.recententlyChangedValue = ko.observable();

//coputed array is upper case which is data-bound to the ui
this.uppercasepeople = ko.computed({
    read: function () {
        alert('read does get called :)...yaaaa!!!');
        return self.lowercasepeople().map(function (element) {
            var o = { name: element.name.toUpperCase() };
            return o;
        });
    },
    write: function (value) {
        alert('It will be called only when you change the value of uppercasepeople field');
        //do something with the value 

         self.recententlyChangedValue(value);             
    },
    owner: self
});
}

JQuery Knockout ComputedObservable写入没有被ObservableArray调用

2 个答案: